clutter-actor: Add detail to captured-event signal

The detail allows handlers to distinguish between high volume cursor motion
events and everything else. This allows (most) event handlers who don't
care about cursor motion to not have their power/CPU usage impacted by it.

Using minimal classification is important because it allows those handlers
who do want to use this optimization via 'captured-event::nonmotion' to keep
supporting multiple event types without requiring any logic changes.

Any handler that does want cursor motion events and others should simply
remain unmodified and keep using 'captured-event'.

This helps with GNOME/mutter#283
3 jobs for !283 with captured-event-detail in 29 minutes and 38 seconds (queued for 16 seconds)
latest detached
Status Job ID Name Coverage
  Review
passed #230263
check-commit-log

00:05:45

 
  Build
passed #230264
build-mutter

00:07:08

 
  Test
passed #230265
test-mutter

00:16:43