Add /Process.Kill RPC endpoint and fix CLI IPv6/port bugs

Add kill to RPCs in process module (#103)

* Add kill to process to send signals to a given pid.

No support for wildcarding with negative pids/signals (too dangerous)

* Client side of kill

* Integration testing for kill.

shfmt also redid some lines

v1.2.0: Add directory field to ExecuteState so we have a place to write (#105)

N other logs a service might generate in response.

Update to g 1.18

v1.1.0

Update to go 1.18 (#102)

v1.0.10

Update dependency packages (#101)

v1.0.9: Add some needed exec options: (#99)

* Add some needed exec options:

Run as a specific user/group
Append specific env vars to the otherwise clean environment.

Tests for everything

* Simplify uid/gid by prepopulating with our euid/gid

v1.0.8: Add support for CLI quality of life updates: (#95)

* Add support for

--targets-file - File with list of targets

Default port settings

$SANSSHELL_PROXY env var

* We're allowed now to just have a proxy and no targets depending on action.

* Fix check to be correct

* Require at least one target and pass it even for changing proxy log level

* Change back to requiring target or proxy

* No use tracking eof state if we don't set it.

Otherwise we loop again and always see EOF and drop the errors we might have gotten.

* Allow no targets so you can still get a Conn to the proxy.

Won't work except for proxy only RPCs like log levels but this makes it avoid passing a needless target

* Fix a typo

* Remove need to set a target for a proxy only action

v1.0.7

Add a cert field to HostAuthInput so we can use a cert from the host …

v1.0.6

Remove ansible from default policy as unsafe to open w/o params. (#84)

v1.0.5: Make sure and import modules in the main.go (#78)

Srop doing this in the common module.

Which modules a server/cli use should be decided by the end builder, not common code.

v1.0.4: Implement a logging module. (#77)

* Implement a logging module.

This can safely set the logging verbosity level on a server using stdr package.

Implement basic unit tests and client/integration tests.

All client side support in sanssh to do this on the proxy itself.

Wire into proxy as an RPC it'll serve in addition to /Proxy.Proxy
This means we need to add interceptors for unary RPCs here now too.

* Rename from logging to sansshell as the service breakdown so it's obvious this is internal state.

* Fix client command to be sansshell instead of logging