Delivering high scroll performance

What this post added

Introduced an on-device strategy for measuring and identifying scroll performance regressions on iOS. This involves using CADisplayLink to measure frame rates and SIGPROF signals to capture call stacks of the main thread when frame drops occur. A high-priority signaling thread is used to ensure timely capture of backtraces during periods of high main thread utilization. The captured backtraces are then symbolicated and aggregated to pinpoint performance bottlenecks.