Track work done during region sampling in surface flinger process

- Track metrics related to duration and count during region sampling.
- Measure the duration from the start of the drawLayers slice in the RE thread, till the end of the waitForever slice in the RegionSampling track.
- Test trace link https://drive.google.com/file/d/1QIhsXUw02k_Goe5Tqi6pQxcJYmtLMkYT/view?usp=sharing

Bug: 439731821
Test: atest SysUiMetricsV2Test
Flag: EXEMPT METRICS
Change-Id: I2934b141c8954c1f57fbf5a7d3af05ab12488e2f