Raise an error when calling an unimplemented db metric operation

What does this MR do and why?

Related to #332553 (closed)

Add a check for database instrumented classes so we can use only implemented operations.

Raise error if an incorrect operation is used.

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How to set up and validate locally

1. Add a new database instrumentation metric class, following the implementation guide.
2. Set the operation of the new class to a symbol not listed on our list of supported db metrics operations
3. The specs for given class should fail, raising the UnimplementedOperationError.

MR acceptance checklist

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