Refresh docs for GitHub Actions usage. (iree-org#18035)

Progress on iree-org#16203 and
iree-org#17957.

New page preview:
https://scotttodd.github.io/iree/developers/general/github-actions/

## Overview

This documents the state of our GitHub Actions usage after recent
refactoring work. We used to have a monolithic `ci.yml` that ran 10+
builds on every commit, many of which used large CPU runners to build
the full project (including the compiler) from source. Now we have
platform builds, some of which run every commit but many of which run on
nightly schedules. Most interesting _test_ jobs are now a part of
"pkgci", which builds release packages and then runs tests using those
packages (and sometimes runtime source builds).

Net results:

* Infrastructure costs should be more manageable - far fewer workflow
runs will require powerful CPU builders
* Self-hosted runners with special hardware have dedicated places to be
slotted in and are explicitly not on the critical path for pull requests

## Details

* Add new README badges
* pre-commit, OpenSSF Best Practices, releases (stable, nightly), PyPI
packages, select CI workflows
* Add github-actions.md webpage
  * Full workflow status tables
  * Descriptions of each type of workflow
  * Tips on (not) using Docker
  * Information about `pull_request`, `push`, `schedule` triggers
  * Information about GitHub-hosted runners and self-hosted runners
  * Maintenance/debugging tips
* Small cleanup passes through related files

skip-ci: modified script does not affect builds

README.md

@@ -11,16 +11,40 @@ constraints and special considerations of mobile and edge deployments.
 See [our website](https://iree.dev/) for project details, user
 guides, and instructions on building from source.
 
-[![CI Status](https://github.com/iree-org/iree/actions/workflows/ci.yml/badge.svg?query=branch%3Amain+event%3Apush)](https://github.com/iree-org/iree/actions/workflows/ci.yml?query=branch%3Amain+event%3Apush)
 [![IREE Discord Status](https://discordapp.com/api/guilds/689900678990135345/widget.png?style=shield)]([https://discord.gg/wEWh6Z9nMU](https://discord.gg/wEWh6Z9nMU))
+[![pre-commit](https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit)](https://github.com/pre-commit/pre-commit)
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/8738/badge)](https://www.bestpractices.dev/projects/8738)
 
 #### Project Status
 
 IREE is still in its early phase. We have settled down on the overarching
 infrastructure and are actively improving various software components as well as
 project logistics. It is still quite far from ready for everyday use and is made
 available without any support at the moment. With that said, we welcome any kind
-of feedback on any [communication channels](#communication-channels)!
+of feedback on any [communication channels](#communication-channels)
+
+#### Release status
+
+| Package | Release status |
+| -- | -- |
+GitHub release (stable) | [![GitHub Release](https://img.shields.io/github/v/release/iree-org/iree)](https://github.com/iree-org/iree/releases/latest)
+GitHub release (nightly) | [![GitHub Release](https://img.shields.io/github/v/release/iree-org/iree?include_prereleases)](https://github.com/iree-org/iree/releases)
+Python iree-compiler | [![PyPI version](https://badge.fury.io/py/iree-compiler.svg)](https://badge.fury.io/py/iree-compiler)
+Python iree-runtime | [![PyPI version](https://badge.fury.io/py/iree-runtime.svg)](https://badge.fury.io/py/iree-runtime)
+
+#### Build status
+
+[![CI](https://github.com/iree-org/iree/actions/workflows/ci.yml/badge.svg?query=branch%3Amain+event%3Apush)](https://github.com/iree-org/iree/actions/workflows/ci.yml?query=branch%3Amain+event%3Apush)
+[![PkgCI](https://github.com/iree-org/iree/actions/workflows/pkgci.yml/badge.svg?query=branch%3Amain+event%3Apush)](https://github.com/iree-org/iree/actions/workflows/pkgci.yml?query=branch%3Amain+event%3Apush)
+
+| Host platform | Build status |
+| -- | --: |
+Linux | [![CI - Linux x64 clang](https://github.com/iree-org/iree/actions/workflows/ci_linux_x64_clang.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_linux_x64_clang.yml?query=branch%3Amain+event%3Apush)<br>[![CI - Linux arm64 clang](https://github.com/iree-org/iree/actions/workflows/ci_linux_arm64_clang.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_linux_arm64_clang.yml?query=branch%3Amain+event%3Aschedule)
+macOS | [![CI - macOS x64 clang](https://github.com/iree-org/iree/actions/workflows/ci_macos_x64_clang.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_macos_x64_clang.yml?query=branch%3Amain+event%3Aschedule)
+Windows | [![CI - Windows x64 MSVC](https://github.com/iree-org/iree/actions/workflows/ci_windows_x64_msvc.yml/badge.svg?query=branch%3Amain+event%3Aschedule)](https://github.com/iree-org/iree/actions/workflows/ci_windows_x64_msvc.yml?query=branch%3Amain+event%3Aschedule)
+
+For the full list of workflows see
+https://iree.dev/developers/general/github-actions/.
 
 ## Communication Channels
 

build_tools/scripts/get_latest_green.sh

@@ -20,6 +20,10 @@ set -euo pipefail
 
 commitish="${1:-HEAD}"
 
+# TODO(scotttodd): update from ci.yml to new list
+#   * linux x64 clang
+#   * linux x64 clang asan
+#   * pkgci.yml?
 declare -r REQUIRED_WORKFLOWS=(ci.yml)
 declare -ar QUERY_PARAMS=(
   branch=main

docs/website/docs/developers/general/contributing.md

@@ -293,20 +293,8 @@ IREE supports building from source with both Bazel and CMake.
 
 ### :octicons-server-16: Continuous integration (CI)
 
-IREE uses [GitHub Actions](https://docs.github.com/en/actions) for CI. The
-primary CI is configured in the
-[ci.yml workflow file](https://github.com/iree-org/iree/blob/main/.github/workflows/ci.yml).
-
-#### Self-hosted runners
-
-In addition to the default runners GitHub provides, IREE uses
-[self-hosted runners](https://docs.github.com/en/actions/hosting-your-own-runners/managing-self-hosted-runners/about-self-hosted-runners)
-to run many of its workflow jobs. These enable access to additional compute and
-custom configurations such as accelerators.
-
-* Configuration for GCP runners is stored at
-[`build_tools/github_actions/runner/`](https://github.com/iree-org/iree/blob/main/build_tools/github_actions/runner/)
-* Configuration for other runners is done manually as needed
+IREE uses [GitHub Actions](https://docs.github.com/en/actions) for CI. See
+our [GitHub Actions documentation](./github-actions.md) for full details.
 
 #### CI behavior manipulation