Refactor CODEOWNERS to point to exact paths to packages

[pokey]

If we are using *foo* in our CODEOWNERS, that is a smell and means our package encapsulation isn't good enough. We should try to move neovim-specific code and keyboard-specific code into well-defined packages and then add those exact paths to our CODEOWNERS

Depends on:

• Add ide-specific test-harness packages #2564