Sroute tool

[Wen-Tian-Pineapple]

Description

As described in #2209 and #2349, in the design that involves multiple voltage domains, there is no routes from standard cell to another voltage domain that is generated by pdngen. We addressed this issue with the pull request using the original detail router. However, as described in #3071 and #3067. There are some problems when using the existed detail router for special route, in order to adress those problems, we proposed a new router seperated from the original one.

Proposed Command:
All of these commands should be called before global route.
add_sroute_inst: collect all the pins that are suppose to get connected with the power domain

add_sroute_connection: [layers] [vias] [net name] [metal width] [metal space]
Currently this command creates custom connections from all the collected pins(using add_sroute_inst) to the power ring before global route.

temp sense generator exmaple 1:

exmaple 2:

Future Work:
Make our tool aware of multiple different physics property of analog circuit and optimize them.