simpleperf: report_html.py: sort functions in flamegraph by their names

It is to generate a stable ordering of functions in flamegraphs.
So the layout will generally match up when comparing multiple reports.

Bug: 306433890
Test: run test.py --only-host-test
Change-Id: Iee13bce421261867d7f609858277752cd6ee4059
2 files changed