Add (& fix) some simple source code checks (#8821)

Add (& fix) some simple source code checks (#8821)

Summary:
* Don't hardcode namespace rocksdb (use ROCKSDB_NAMESPACE)
* Don't #include <rocksdb/...> (use double quotes)
* Support putting NOCOMMIT (any case) in source code that should not be
committed/pushed in current state.

These will be run with `make check` and in GitHub actions

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8821

Test Plan: existing tests, manually try out new checks

Reviewed By: zhichao-cao

Differential Revision: D30791726

Pulled By: pdillinger

fbshipit-source-id: 399c883f312be24d9e55c58951d4013e18429d92