[VRR] Clear frame rate and category after 750ms idle

This reverts commit 6a0a927a, but changes the required idle time to 750ms so that blinking cursors are not affected.

Change-Id: Idf7865b47c0b0bdac2b63d7174316c4d6be70d4f
Test: v2/android-crystalball-eng/health/microbench/systemui/systemui-foldable-latency-suite
Test: v2/android-crystalball-eng/health/microbench/systemui/main/systemui-quicksettings-1-jank-suite