renderer/native: Add tracing for 2nd GPU copies

These traces allow seeing how long the copy operations stall in libmutter, and
which copy operations actually get used.

GNOME/mutter!615
4 jobs for !615 with mr/primary-copy in 8 minutes and 7 seconds (queued for 2 seconds)
detached
Status Job ID Name Coverage
  Review
passed #332053
check-commit-log

00:00:40

 
  Build
passed #332054
build-mutter

00:01:31

 
  Test
passed #332056
can-build-gnome-shell

00:05:55

passed #332055
test-mutter

00:02:34