Add a QueryRecorder for Gitaly calls

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Right now, we're only counting the number of Gitaly calls in the request store to raise errors if a request exceeds a certain limit.

We can leverage that in specs already, but it's quite cumbersome.

We should add a GitalyCallRecorder with a set of matchers that keeps track of Gitaly calls in specs so we can count calls and compare calls so we can avoid N+1s in unit tests.