Add a linter to detect usage of contexts with timeouts from parent tests in subtests that call `t.Parallel`

[ethanndickson]

This comes up somewhat frequently and results in flakey tests:
coder/coder#19330
coder/coder#19029
coder/coder#18872
coder/coder#15314

The issue is described in detail in Spike's blog post. We should explore how we can check this as part of linting. It'd be cool if we could then add this to a metalinter like golangci-lint.

[ethanndickson]

Started working on this @ https://github.com/coder/paralleltestctx