Fix [#34716] Change Trim Duration (soft) value nothing happening. until mouse drag footage(image sequence)

As those two properties do not need a custom set func, yet need recalc of strips drawing/positions in addition to usual rna_Sequencer_update() (cache invalidating), I renamed rna_Sequence_frame_change_update to do_sequence_frame_change_update, and made a new rna_Sequence_frame_change_update which is directly usable as RNA update func, and call both the strip and cache update funcs.

Thanks to Sergey for advices!

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55573 954f8c5b-7b00-dc11-b283-0030488c597c