Add bytes fetched in query frontend #129

Job	Run time
Linters (Static Analysis) for Go	1m 53s
Thanos end-to-end tests (8, 0)	4m 0s
Go build for different platforms	7m 56s
Thanos unit tests	17m 33s
Thanos end-to-end tests (8, 1)	2m 53s
Thanos end-to-end tests (8, 2)	2m 42s
Thanos end-to-end tests (8, 3)	3m 36s
Thanos end-to-end tests (8, 4)	6m 28s
Thanos end-to-end tests (8, 5)	3m 19s
Thanos end-to-end tests (8, 6)	3m 19s
Thanos end-to-end tests (8, 7)	3m 10s
	56m 49s

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