Rename PipBoundsHandler to PipBoundsAlgorithm

Now that all state handling has been moved out of
PipBoundsHandler, this CL renames it to
PipBoundsAlgorithm and cleans up its public API
so that it functions more like an utility to
calculate several types of "bounds" related to PIP
such as:
- Default bounds
- Normal bounds
- Movemement bounds
- Entry bounds
- Bounds adjusted to aspect ratio
- Inset bounds

PipBoundsAlgorithm's is then only responsible for
calculating such bounds based on the current state of
PIP (owned by PipBoundsState) but it no longer owns
or manages the state, as that would be the
responsability of its users (e.g PipController).

Bug: 169373982
Test: atest com.android.wm.shell.pip
Change-Id: I67c3004b60069160f82d7c3d00d8c3995c0c5f80