refactor(bigtable): clean up public query classes #8674

Job	Run time
debug_job	2s
Save PR ref	4s
Windows-CMake / cmake + msvc-2022 + x64 + Release + Core4	11m 52s
Windows-CMake / cmake + msvc-2022 + x64 + Release + Core3	9m 49s
macOS-CMake	0s
macOS-Bazel	0s
Windows-Bazel	0s
Notify-Google-Chat	4s
	21m 51s

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