[FEATURE] 😶 Add `NullFusionCache` support via DI

[jodydonetti]

Problem

Community user @eskild-th noted in #440 that using NullFusionCache via DI is not that easy. But it should be.

Solution

I'm adding a new builder method WithNullImplementation() that creates a NullFusionCache instance instead of a standard FusionCache one.

All the builder methods must work even when using the null implementation, including the HybridCache support stuff, and everything else should stay the same.

[jodydonetti]

Hi all, v2.2.0-preview-1 is out 🥳

[jodydonetti]

Hi all, v2.2.0 is out 🥳
And for the corresponding LTS-only release, there's v2.0.2.