Refactor: Pull tracing out of TimeStats.

The tracing in TimeStats ended up having no actual overlap with current
TimeStats functionality. This CL pulls all tracing related code out
into its own class.

Test: atest libsurfaceflinger_unittest and manually inspected traces.

Run trace with:
{ adb shell perfetto -c - --txt -o /data/misc/perfetto-traces/trace <<EOF
buffers: {
    size_kb: 1280
}
data_sources: {
    config {
        name: "android.surfaceflinger.frame"
    }
}
duration_ms: 3000
EOF
} && adb pull /data/misc/perfetto-traces/trace ~/Desktop/trace

Fixes: 140298240
Change-Id: I52d80d46eb8dee8979b02416ab7a758b7e58dfd1