validator: Add CLI args to control rocksdb threadpool sizes #15494

Job	Run time
cargo-test-sbf (token/program)	7m 25s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	12m 2s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	7m 59s
cargo-test-sbf (token-upgrade/program)	13m 43s
cargo-test-sbf (feature-proposal/program)	11m 43s
cargo-test-sbf (governance/addin-mock/program, governance/program)	9m 48s
cargo-test-sbf (name-service/program)	8m 8s
check	2m 59s
cargo-test-sbf (stake-pool/program)	10m 34s
cargo-test-sbf (single-pool/program)	7m 46s
test (token/cli, token/program, token/program-2022, associated-token-account/program, instruction...	18m 38s
test (single-pool/cli, single-pool/program)	14m 39s
test (token-upgrade/cli, token-upgrade/program)	13m 50s
	2h 19m 14s

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