127458147: Include IntDef annotations in current.txt

Adds a new mode, off by default, which lets you either include
typedef annotation references in the signature files (without
the typedef classes themselves), or inline the typedef constants
themselves into all the annotated sites.

Usage:
--typedefs-in-signatures <ref|inline>
     Whether to include typedef annotations in
     signature files. `--typedefs-in-signatures ref`
     will include just a reference to the typedef
     class, which is not itself part of the API and
     is not included as a class, and
     `--typedefs-in-signatures inline` will include
     the constants themselves into each usage site.
     You can also supply `--typedefs-in-signatures
     none` to explicitly turn it off, if the default
     ever changes.

Bug: 127458147
Test: Unit tests included
Change-Id: I9aee3043fb7d0a12bebe23e02ecce405723478f0