impl(bigtable): improve QueryPlan and add more tests #8557

Job	Run time
debug_job	3s
Save PR ref	3s
macOS-CMake	0s
Windows-CMake / cmake + msvc-2022 + x64 + Release + Core3	9m 30s
Windows-CMake / cmake + msvc-2022 + x64 + Release + Core4	12m 29s
macOS-Bazel	0s
Windows-Bazel	0s
Notify-Google-Chat	3s
	22m 8s

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