Handle update of mutable descendants of immutable fields in Update #23893
Description
What kind of contribution is this issue about?
MMv1-based resource
Details
Per our docs, immutability isn't inherited from field to field - that is, if a parent field is immutable, a child field can still be updatable in-place. This works as expected in terms of the schema, but the update method template currently ignores immutable fields (which means that we don't recurse to handle child fields that are updatable in place). It looks like there are 64 fields across the provider impacted by this behavior.
Note: update_url doesn't seem to be a workaround for this, since we only actually support update_url on root fields.
References
Ran across this while investigating #23823. In this case, the top-level field was incorrectly marked as immutable - however, it's unclear whether that will always be the case.