Caching.StackExchangeRedis: add "force reconnect" pattern (#45261)

* 1. add "force reconnect" pattern via OnRedisError
2. avoid thread-race problems by having Connect[Async] *return* the cache, rather than relying on field
3. avoid thread-race problems by only using a single ref field (cache), rather than cache+muxer; access indirectly
4. use more efficient key-prefix path via RedisKey.Append
5. use more efficient hash-fetch by pre-storing the hash-key arrays (removes need for RedisExtensions.cs)
6. general code tidy; null-handling, defaults, etc (no semantic change)

* copy the time-based force reconnect logic from azure redis cache best practices

* remove a couple of dead comments

* PR feedback

* clarify timing

* Update src/Caching/StackExchangeRedis/src/RedisCache.cs

Co-authored-by: Stephen Halter <[email protected]>

* Update src/Caching/StackExchangeRedis/src/RedisCache.cs

Co-authored-by: Stephen Halter <[email protected]>

* 1. nits
2. add new UseForceReconnect option

* rev SE.Redis to 2.6.90, which has improvements to connection stability

* remove UseForceReconnect, preferring an app-context switch

* PR feedback; move the AppContext check to RedisCacheOptions

* - fixup NRT warnings (also uses ROM-byte support by default now)
- fixup interface delta in test harness
- make an analyzer happy about a redundant lambda

* Update src/Caching/StackExchangeRedis/src/RedisCache.cs

Co-authored-by: David Fowler <[email protected]>

* fixup PR drift

* fix NRT

---------

Co-authored-by: Stephen Halter <[email protected]>
Co-authored-by: Sébastien Ros <[email protected]>
Co-authored-by: David Fowler <[email protected]>

Author: 4 people

eng/Versions.props

@@ -288,7 +288,7 @@
     <SeleniumWebDriverVersion>4.7.0</SeleniumWebDriverVersion>
     <SerilogExtensionsLoggingVersion>1.4.0</SerilogExtensionsLoggingVersion>
     <SerilogSinksFileVersion>4.0.0</SerilogSinksFileVersion>
-    <StackExchangeRedisVersion>2.2.4</StackExchangeRedisVersion>
+    <StackExchangeRedisVersion>2.6.90</StackExchangeRedisVersion>
     <SystemReactiveLinqVersion>5.0.0</SystemReactiveLinqVersion>
     <SwashbuckleAspNetCoreVersion>6.4.0</SwashbuckleAspNetCoreVersion>
     <XunitAbstractionsVersion>2.0.3</XunitAbstractionsVersion>