Create a linter to support the Speculative Feature Framework

[dannykopping]

https://www.notion.so/coderhq/Speculative-Feature-Framework-223d579be5928051b865d4e9572c8d23?source=copy_link

We need a linter which must raise when:

• an experimental package is imported
• the ExperimentalClient is used (to call an experimental API)

Note: coder/coder#19950 took an initial stab at some of these requirements, but it went stale and @spikecurtis' proposal should be revisited.