[VRR] Reset frame rate category as DEFAULT

Reset frame rate category as DEFAULT in ViewRootImpl.performtraversals() so that we won't call setFrameRateCategory if no Views vote for a category. Also, Views can also vote for NO_PREFERENCE now.

Moreover, update the required Flag in some of the test in ViewRootImplTest
from FLAG_TOOLKIT_FRAME_RATE_FUNCTION_ENABLING_READ_ONLY to FLAG_TOOLKIT_FRAME_RATE_VIEW_ENABLING_READ_ONLY

Bug: 334114192
Test: atest ViewRootImplTest / ViewFrameRateTest
Change-Id: I4894d3462db329ef852f944e8a1b2bbf18b2bab6