feat(spanner): add settings for gRCP keep-alive #22507

Job	Run time
bulk-filter	1m 12s
windows	2m 14s
changes	29s
units (8)	1m 31s
gapic-libraries-bom	20m 49s
lint	3m 22s
units (21)	41s
enforcer	20m 26s
units (17)	42s
units (25)	50s
units (26)	55s
units (11)	57s
split-clirr (java-spanner)	2m 18s
split-units (java-spanner, 21)	4m 47s
split-units (java-spanner, 11)	3m 41s
split-units (java-spanner, 8)	4m 37s
split-units (java-spanner, 25)	4m 41s
split-units (java-spanner, 17)	4m 49s
split-units (java-spanner, 26)	4m 38s
split-dependencies (java-spanner)	3m 54s
conditional-required-check	4s
	1h 27m 37s

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