Ref: #132179
Renames:
- `Editing.act_seq` -> `Editing.act_strip`
- `SequenceModifierData` -> `StripModifierData`
- Its member `mask_sequence` is now `mask_strip`.
- `MetaStack.parseq` -> `MetaStack.parent_strip`
- Remaining function names/parameters that were not dealt with in #132748
- Various references to `seq` or `sequence` throughout code and docs when
referring to a strip
Also moves `_get` to the end of the renamed function names where
applicable for standardization (unless "by" or "from" are used).
There should be no changes to current behavior.
Pull Request: https://projects.blender.org/blender/blender/pulls/138077
2ab59859c9