Assert store-gateway path in compression test

[Rohithmatham12]

What this changes

• Waits until the store-gateway has loaded the shipped block, not only until a bucket sync has happened.
• After querying the shipped series, asserts that the querier recorded a /gatewaypb.StoreGateway/Series client request.
• This makes the store-gateway compression subtest prove it exercised the -querier.store-gateway-client.grpc-compression path.

Fixes #7583.

Testing

• GOCACHE=/private/tmp/cortex-go-cache GOMODCACHE=/private/tmp/cortex-go-mod-cache go test -tags requires_docker,integration,integration_grpc ./integration -run TestGRPCCompression -count=0