[Enum Shorthands] Core library updates

[kallentu]

This issue tracks the changes we want to make to the core libraries with the enum shorthands feature.

I believe we'll have a lint that converts typed static accesses to enum shorthand form (Color.blue -> .blue). Do we want to change any part of the core libraries to use enum shorthands?
And any other changes we need to make?

cc. @lrhn

[lrhn]

There is no urgency.
This is a shorthand that only affects readability of implementation code, not the API. Nobody should be able to see, or care, whether we use the shorthand or not.

We can choose to use it everywhere it applies, as a style statement, or we can update code when we touch it anyway.
The latter has been our strategy so far, so let's just keep doing that.

[kallentu]

Sounds good to me.