Fix tests for handwriting initiator changes

ag/26416134 updated the handwriting initiator to track EditTexts even if
handwriting is disabled, which broke some tests. This change updates
HandwritingAreaTrackerTest and HandwritableViewInfoTest to use Views
instead of EditTexts.

Bug: 297962571
Bug: 330568768
Test: atest HandwritingInitiatorTest
Test: atest HandwritingAreaTrackerTest
Test: atest HandwritableViewInfoTest
Change-Id: Iedc68d4f7db9a71bd0ef98b48cf982101c0a2e45