Lint to identify "deprecated at birth" APIs.

When API council requests changes, teams regularly perform the
requested refactoring, but simply mark the old APIs as @Deprecated
without @removed, due to internal users.

As part of finalizing an SDK, we should ensure that no new APIs are
marked @Deprecated, since they're typically cleanup that someone
forgot to finish.  This extension to the lint script makes it easy
to identify these cases.

$ python tools/apilint/apilint.py --show-deprecations-at-birth \
        api/current.txt ../../prebuilts/sdk/api/28.txt

$ python tools/apilint/apilint.py --show-deprecations-at-birth \
        api/system-current.txt ../../prebuilts/sdk/system-api/28.txt

Bug: 77588754
Test: manual inspection
Change-Id: Ie9658006bb08f780bee0e503481d3bafec1038a1