Improve how we exempt resources from getting their names collapsed.

Removed the --whitelist-path flag, which is poorly named and we can
already specify these resources with --resources-config-path.

Renamed TableFlattenerOptions.whitelisted_resources to keep_resources.
It holds ResourceName instead of std::string. This lets us include type
when specifying what gets exempted, for correctness.

Bug: 111115201
Test: make aapt2_tests
Change-Id: Ifa5df924b5e2265c32cdcf8ca7dfa4a3992a0468