Auto merge of #13043 - Jarcho:assign_clone, r=Manishearth

Refactor `assigning_clones`

Short list of changes:
* Inline and simplify `extract_call`
* Inline `is_ok_to_suggest`
* Inline `skip_drop_block`
* Check the HIR tree before the macro check
* Don't call `outer_expn_data`
* Use `find` instead of a loop in `clone_source_borrows_from_dest`

changelog: none

Author: bors