Strip locking was meant to be used with strip transformation only. So
the check, whether strip is locked is removed from hide/unhide operator.
Further it was requested to lock sound strip subframe offset. Since this
is time related property, it was moved to time panel. This also
addresses request to make it more obvious, why the value can't be
changed.
The name of the property was clarified from "Offset" to
"Sound offset", because there are another 2 offsets in the panel.
Finally, when channel is locked, properties in side panel now reflects
this state. This is done by adding RNA get function for `Strip.lock`
property. Function `seq::transform_is_locked` is used instead of
checking `SEQ_LOCK` flag, because it also checks channel state. With
this setup, the lock property can't be disabled while channel is locked.
However strip lock flag will be unset, which can be prevented. (I am not sure which is better. Both are fine in my eyes.)
Pull Request: https://projects.blender.org/blender/blender/pulls/135831
0b633fab3e