[Mypy] fix other/least_recently_used (#5814)

* makes LRUCache constructor concrete

* fixes bug in dq_removal in other/least_recently_used

+ deque.remove() operates by value not index

* [mypy] Annotates other/least_recently_used over generic type

+ clean-up: rename key_reference to match type.

* [mypy] updates example to demonstrate LRUCache with complex type

* Adds doctest to other/least_recently_used

* mypy.ini: Remove exclude = (other/least_recently_used.py)

* Various mypy configs

* Delete mypy.ini

* Add mypy to .pre-commit-config.yaml

* mypy --ignore-missing-imports --install-types --non-interactive .

* mypy v0.910

* Pillow=8.3.7

* Pillow==8.3.7

* Pillow==8.3.2

* Update .pre-commit-config.yaml

* Update requirements.txt

* Update pre-commit.yml

* --install-types  # See mirrors-mypy README.md

Co-authored-by: Christian Clauss <[email protected]>