Change API format in the map file.

* Parameter list should be a part of the API signature.
* Package, class, and method names are stored separately so they don't
  need to be parsed when being read.

Bug: 315412454
Test: mmm -j frameworks/base/api/coverage/tools/:extract-flagged-apis
      extract-flagged-apis <input api.text file> <output pb file>
Change-Id: I769cc10831f1c50c71e71cbaadec355f21258baf