Adding slang as SystemVerilog linter

[astrollo]

The feature is not related to a problem

Describe the solution you'd like
It would be nice to include slang (https://github.com/MikePopoloski/slang) as an additional linter to teros HDL. Currently, slang is the most compliant SystemVerilog open source frontend.

[AndrewNolte]

I think slang is best positioned to be the best option for analyzing verilog because of speed and compliance. It could also be used to analyze drivers/loads, dependency tree, etc. Right now this can sort of be achieved through tying together scripts (see this exension), but I think it would be best if a proper language server were made with slang, rather than a bunch of binaries.