Extract default freeform bounds logic from TaskLPM

This CL extracts getDefaultFreeformBounds from TaskLPM into a
new utility class so it can be used in other LPMs.

The behavior doesn't change except for:
- making the stable bounds and default size overridable.
- allowing usnig different default sizes depending on the
 orientation.

Bug: 185427982
Test: manual
Change-Id: Ie31bae7efdf338db76b482702b7b385ba6667b65