Make LockPatternView dot hit area circular.

Dot hit area is rectangular. Make it circular to be able to increase the area and preserve diagonal connections.
Cover with tests to ensure that touches handled correctly.

Bug: 204870856
Bug: 215183631
Tests: LockPatternViewTest and manualy on watch and phone
Change-Id: I7d7b539afcdd4d86cb8f828030a2f4866963f8aa
4 files changed