Add tools to generate compile_commands.json

[lixin-wei]

Why are these changes needed?

We want to use clangd as the language server.

clangd is an awesome language server that has many features and is very accurate.

But it needs a compile_commands.json to work.

This PR adds a popular bazel rule to generate this file.

Checks

• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[mwtian]

Looks good. compile_commands.json would be useful for tools like clang-tidy as well.

[lixin-wei]

The failed tests seems not related. Could you please merge this PR?