Fix autohide glitches explainations

Make previous commit a bit clearer, so check commit a62b48b for
actual code changes.

Use _hide and _show to improve readability and keep control over
transition behaviours. Only thing is, it now uses the extension's
animation delay settings.

Keeping the _box.hover check in an else statement guarantee other docks
that do not use _onPressureSensed will keep the same behaviour.
Because of this, I think setups using intellihide/autohide without
the push-to-show option (most likely) will still have the bouncing
glitch issue.

Delete the _delayedHide value in _show instead of _animateIn since calls
to said _show are ignored when the dock's state is either "shown" or
"showing" and, when a delayed hide transition is queued, the dock's state
is only updated AFTER the animate-in transition is completed.

Replace the _hide call to _hoverChanged the same way shouldHide was (is)
used in _onPressureSensed to catch any _delayedHide shenanigans by checking
whether the delayed animate-out transition is still necessary instead of
forcing the dock to hide right away and trigger a bounce from _box's
hover-changed signals.

Fixes #1232