[HybridCache] [Behavior Proposal] Allow Options from GetOrCreateAsync to not set "null" in cache

Hello,

As far as I've tested, it seems that when a CACHE MISS happen the "Create Factory" is called.
When this happen and the factory also returns `null` (like for example `db.FirstOrDefault(id)`, then the `null` value is also propagated to the cache.

This create quite some noise for cached object lifetime managment.

It would be nice to be able to pass a value inside the already existing `Options` parameter of the `GetOrCreateAsync` that tells the factory:
"If the factory returns `null`, don't bother settings `null` in cache"