Clean up visibility related flags in ActivityRecord

- Replace visible and hiddenRequested flag by a single flag
  mVisibleRequested.
- Merge setVisible() into setVisiblity().

Test: Refactoring, all existing tests pass.
Bug: 80414790
Change-Id: I7bafdb86e6b8431046775d3968d24f85c3fac45a
21 files changed