add set_sysvar_for_tests to SysvarCache #7382

Job	Run time
cargo-test-sbf (token/program)	8m 3s
check	2m 12s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	13m 43s
test (token/cli, token/program, token/program-2022, associated-token-account/program, instruction...	21m 35s
test (single-pool/cli, single-pool/program)	19m 13s
test (token-upgrade/cli, token-upgrade/program)	16m 23s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	10m 27s
cargo-test-sbf (token-upgrade/program)	8m 15s
cargo-test-sbf (feature-proposal/program)	7m 46s
cargo-test-sbf (governance/addin-mock/program, governance/program)	13m 10s
cargo-test-sbf (memo/program)	7m 52s
cargo-test-sbf (name-service/program)	7m 24s
cargo-test-sbf (stake-pool/program)	11m 43s
cargo-test-sbf (single-pool/program)	8m 25s
	2h 36m 11s

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