`SequencesMeta.new_movie()` API function caused meta strip to change
length. Similar issue has been fixed in transform code by checking
if `MetaStack` exists. `MetaStack` is not used when changing data in
python.
Provide `seqbase` to `SEQ_time_update_sequence()` so the function can
check if change happens inside of meta strip.
This patch also merges `seq_time_update_sequence_bounds()` into
`SEQ_time_update_sequence()`. This is because same issue applies for
both functions and it is confusing to have more time update
functions.re if this will lead anywhere.
Reviewed By: sergey
Differential Revision: https://developer.blender.org/D12763
877ba6b251