swift234

[Import as member] Turn on CoreGraphics.

Introduces CoreGraphics.apinotes, in which we enable the
import-as-member inference system. Additionally, include some explicit
SwiftNames, for when inference doesn't produce the right result, and
to aid compatibility with the overlays.

Refactors many of the trivial overlays out, shrinking the
CoreGraphics.swift overlay by over half. Updates in-tree test
cases. The names we currently have will be highly in flux for a while,
and are likely to change frequently over the near term.

There are a few remaining known bugs that are worked around by
apinotes entries.