Performance updates to SimpleCache, session cache, cache middlewares

[fselmo]

What was wrong?

Some performance considerations for when to lock the cache.

• Return the cached value at the same time as the evicted_items rather than reaching back into the cache for it. There's no reason to reach back into the cache for it.
• Only lock the cache when necessary. I think we were locking the cache a bit too early in almost all cases here. One exception is the async session cache since a session that is cached can be considered stale. That case was left alone as it should be under lock the whole time.

How was it fixed?

• Lock cache only when necessary.
• Return the cached value from SimpleCache at the same time as the evicted items.

Todo:

• Add entry to the release notes

Cute Animal Picture

My beloved former pigmy goat, Bootsy, as a kid:

[pacrob]

lgtm!