Fix Drupal::cache() forces users to explictly create a service for each binary

Problem/Motivation

In drupal 7 one could consume cache binaries on the fly without having to declare them anywhere:

cache_get(cid, 'whatever');

If you try to do the same thing in Drupal 8, you get a service not found exception:

\Drupal::cache('whatever')->get($cid);

Yes you can still retrieve the cache factory service and ask for a binary.... but that's cumbersome. The first time you get this exception it's a WTF as to why should I explictly have to create a service for each binary.

Proposed resolution

Try to find the cache service, and if it does not exist, fallback to using the cache_factory service to request a binary.

Remaining tasks

User interface changes

None.

API changes

None.

Data model changes

None.