Define broadcast radio HAL 2.0.

The new HAL is a cleanup of 1.x branch of the legacy burden:
 * structure flattened (multi-level factory removed);
 * only one hardware tuner per HAL instance, only one session;
 * front-end app doesn't control region settings anymore;
 * metadata limited to int and string values;
 * removed deprecated methods;
 * result codes redefined.

It also fixes minor mistakes made with HAL 1.1:
 * ProgramSelector simplified;
 * there is no need to control background scan.

There are three features missing compared to the HAL 1.1, as they
are in development with the new design (see design docs attached):
 * Announcements - b/68045105
 * Program list - b/69860743
 * Region handling - b/69958423

Test: VTS
Bug: b/69958777
Change-Id: I0ad83f25630c1250d73dc3941144d345339fbde0