Keep parameter values out IMemoryCache in RelationalCommandCache

[yinzara]

Only store necessary info for parameter values RelationalCommandCacheKey to prevent memory leaks.

This a relatively serious memory leak defect and needs to be ported back to the release/8.0 branch as well.

Fixes #34028

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[roji]

Thanks @yinzara, this looks like a good fix - see minor comments below.

[yinzara]

All done now. Sorry about all the force pushes :)

[yinzara]

All requested modifications have been complete. All checks have passed. Ready for merge when you are.

I know that this defect has technically existed for many prior versions of .NET.

Do we still port defects to the release/6.0 branch or is that branch now completely unmaintained?

Can I help in doing that or is this something only you guys do?