Store the cache alias on the cache backend instance

[Tim Schilling]

Store the alias used to fetch a cache backend instance on the instance itself. The Django Debug Toolbar is having to do some extra patching (django-commons/django-debug-toolbar#2219) to retain what alias is being used for which cache. While tolerable, it means the toolbar is having to reimplement more parts of Django, making it more brittle for future versions.

django/new-features: ​https://github.com/django/new-features/issues/95

Ideal code:

from django.core.cache import cache

print(cache.alias)
# "default"

I believe we need to make the following changes:

• Update CacheHandler.create_connection to pass alias as backend_cls(location, params, alias=alias)
• Update django.core.cache.backends.base.BaseCache.init to accept and store alias

[Jacob Walls]

See you in #36830!