Ensure that fuzz tests compile in CI

[Darksonn]

We don't run fuzz tests in our CI because they're executed elsewhere, but we should still make sure that they compile. To close this, submit a PR that updates our CI configuration to ensure that fuzz tests compile. The CI configuration can be found in the .github directory.

There are a few warnings in the fuzz tests currently, those should be fixed too.

See #5392 for context.

[nathaniel-brough]

There is a github action for oss fuzz that can make this pretty simple. https://google.github.io/oss-fuzz/getting-started/continuous-integration/

[hootio]

Submitted #5670 for checking the /tokio/ subdir.
Was going to include /tokio-stream/ too but that had its own compilation warnings, which should be addressed in a separate PR.

[hootio]

Submitted #5675 to remove compilation warnings from /tokio-stream/. Next step is to add the compilation check step in CI and then this issue can be resolved.

[hootio]

Submitted #5682. Once merged, this issue can be resolved.