Associate the DatabaseRoot with the scoped options instance and not the singleton options.

[koenigst]

• Remove the DatabaseRoot from the InMemoryOptionsExtension service provider equality condition.
• Remove the DatabaseRoot from the InMemorySingletonOptions.
• Resolve the IInMemoryStore in a scoped service (IInMemoryStoreProvider) instead of a singleton service (IInMemoryStoreCache).
• Fall back to the DatabaseRoot stored in a singleton service (IInMemoryDatabaseRootCache) if the options does not specify one.

Fixes #34476