Register "short" and "long" cache services

Register "short" and "long" cache services

Overview
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This is an improvement for developer-experience when working with caches.
It reduces the amount of boilerplate required for core-code or
extension-code in a typical caching use-case.

Before
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* To use a short-lived/latency-optimized cache (e.g. Redis or PHP array),
  you can work with the default cache instance (`Civi::cache('default')`.
* To use a long-lived/durability-optimized cache (e.g. Redis or SQL), there is no
  simple way or code. You must [register a custom cache service](https://docs.civicrm.org/dev/en/latest/framework/cache/#example-named-service).

After
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* All the above remains true. Additionally, you can request the `short` or `long` cache service.
* To use a short-lived/latency-optimized cache, you can use `Civi::cache('short')`. (`short` and `default` are synonmyms.)
* To use a long-lived/durability-optimized cache, you can use use `Civi::cache('long')`.

Comments
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* After this is approved, we should update the [dev docs for caching](https://docs.civicrm.org/dev/en/latest/framework/cache/).
* There's a bike-sheddy argument about the naming. I'd be willing to rename if there was a strong reason, but I don't really think
  there is a strong reason. This naming convention provides a simple dichotomy of `short` vs `long`.