Use lookup string callback function for `sequences_all` RNA property
`rna_SequenceEditor_sequences_all_lookup_string` using a GHash for faster lookups.
When names are changed or strips are added/removed the lookup is tagged invalid.
The next time the lookup is used it will rebuild it.
Reviewed By: sergey, jbakker
Differential Revision: https://developer.blender.org/D11544
There were multiple cases that could lead to problems like moving meta
strip into itself or into it's children meta strips.
Print error string to console when invalid action is requested.
This function can be used to move strips into meta strips with no
side effects like change of selection state.
Reviewed By: ISS
Differential Revision: https://developer.blender.org/D10759
