Blender Git Loki

Cleanup: Sanitise return value of `ED_object_parent_set()`

Return `false` from `ED_object_parent_set()` when parent and child are
the same object. This would break the parenting operator, as returning
`false` stops its loop over all selected objects. This tight coupling
caused T82312.

The loop now has its own check for this, so that it properly continues,
and the implementation of `ED_object_parent_set()` is decoupled from its
surrounding code.

No functional changes.