Fully qualify @attr reference to android.R field

Currently, Metalava has some special handling of '@attr ref R.<field>`
references to make sure that they are fully qualified, i.e.
`@attr ref android.R.<field>`. That special handling complicates
Metalava and is blocking some flagged API work so will be removed.
Before that can be done, the existing incorrect documentation needs to
be cleaned up.

This change cleans up those cases in this repo.

Bug: 371997321
Test: Run `m offline-sdk-docs` before and after to make sure that
      there are no differences.
Flag: DOCS_ONLY
Change-Id: Ic97f01b90193d058d65e6d3c6d0a04ce5e55d7c7