program-test: Fix warp and staking issue (#16002)

Since program-test creates a test genesis and then adds fees and rent,
some of the genesis accounts get rent-collected after warping.  Most
notably, `StakeConfig` gets rent-collected, causing any stake operations
to fail after warp.  This fix creates genesis with the `Rent` and
`FeeRateGovernor` actually used by the bank.

program-test/tests/warp.rs

@@ -164,6 +164,8 @@ async fn stake_rewards_from_warp() {
     let program_test = ProgramTest::default();
 
     let mut context = program_test.start_with_context().await;
+    // warp once to make sure stake config doesn't get rent-collected
+    context.warp_to_slot(100).unwrap();
     let mut instructions = vec![];
     let validator_keypair = Keypair::new();
     instructions.push(system_instruction::create_account(