RFC: Do not export internal constants or constant files from library

[DRiFTy17]

We have typically always exported all modules from Forge, which can have the side-effect of exposing APIs that were only intended for internal use. We've seen this specifically with our "constants" files that most components have. This is where we place static constant values as well as types and interfaces.

Rather than exposing these constants, we should be more explicit about which modules they are placed in and whether they are exported or not. This will allow for us to make internal changes changes more easily when we need to adjust these constants, without worrying if consumers are relying on them.

As we migrate to Lit and simplify our component architecture, these constants files will likely become less and less used (if at all).