BubbleController test for logging drag events

Bubble bar location change logging tests are flakey in BubblesTest.
Move the tests to their own unit test class.

Bug: 380105229
Flag: EXEMPT updating tests
Test: atest WMShellRobolectricTests:com.android.wm.shell.bubbles.BubbleControllerBubbleBarTest
Test: atest WMShellMultivalentTestsOnDevice:com.android.wm.shell.bubbles.BubbleControllerBubbleBarTest
Change-Id: I37fc6742b6ad45f292cfec806b4c041e4ed140b1