Keep actual parameter values out of CommandCacheKey in RelationalCommandCache

[cliffankh0z]

Memory leak when storing the actual parameter values in MemoryCache in CommandCacheKey. Parameter values can be anything used as parameteres for the queries; lists of Guids, even objects used for entity inits etc. This keeps them from being garbage collected and thereby creating memory leaks. Store only what we actually need to compare parameter values.

Anyway, the intent of the code is clear. If a maintainer could fix this in the correct manner and style that would be greatly appreciated!

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        Summary of the changes
        - Store only the data we need

        Fixes #34028

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#34028

[cliffankh0z]

@dotnet-policy-service agree

@dotnet-policy-service agree

[cliffankh0z]

parameterValues contains all user data objects in queries before AsEnumerable or ToList, handle as radioactive. We only need meta data anyway

[cliffankh0z]

It may not seem much, but this a confirmed problem in production for us. Clearing IMemoryCache instantly drops memory by 600mb in some cases. If you are unlucky and a huge query is executed while creating this cache entry for the first time, all those entities will remain in memory through some wierd links that GC deems still alive objects.
In huge codebases it is hard to discern which queries are problematic, as all parameter values in IQueryable, before AsEnumerable or ToList is called will we considered parameterer values here. Sometimes the argument / parameter value can look like IEnumerable-Guid- and look benign, but it is actually a selection on some other entites, so those are now put into IMemoryCache.
But EF Core should handle query parameters with gloves anyway and not chain them up in a memory cache when we only need meta data on the parameters.

To debug the issue we used optionsBuilder.UseMemoryCache(_memoryCache); to easily be able to inspect the same IMemoryCache as EF uses

[cliffankh0z]

Keep old behaviour, where we return true on first object[], or compare all values?