[WIP] ESLint Config Migration: Expand import/no-internal-modules allowlist

[filmaj]

Summary

This is a PR that should be merged into #1024 and incrementally addresses #842.

This PR expands the list of source directories that one may reach into its subdirectories to import individual submodules (details about the `import/no-internal-modules rule here).

The src/receivers directory has no single export - so I think it is safe to allow it there (similar structure to src/middleware). I am less sure of the src/types directory. What do you think @misscoded ?

Impact

Before

✖ 362 problems (173 errors, 189 warnings)
  76 errors and 0 warnings potentially fixable with the `--fix` option.

After

✖ 350 problems (161 errors, 189 warnings)
  76 errors and 0 warnings potentially fixable with the `--fix` option.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[seratch]

src/index.ts has * exports from types/index.ts. Thus, I think this should be fine