cogl: Remove midscene tracking

Midscene tracking was used at a time that some Cogl users
could call random OpenGL API without going through Cogl.
That is not allowed anymore, and certainly not done by
Mutter and GNOME Shell.

Remove midscene tracking from CoglFramebuffer.

!402
5 jobs for !402 with gbsneto/software-picking in 6 minutes and 13 seconds (queued for 7 seconds)
detached
Status Job ID Name Coverage
  Review
passed #353233
check-commit-log

00:00:24

 
  Build
passed #353234
build-mutter

00:02:05

passed #353235
build-without-native-backend

00:02:35

 
  Test
passed #353237
can-build-gnome-shell

00:01:42

passed #353236
test-mutter

00:03:13