Context

pallet-staking-async tests currently allow disabling the post-test invariant check via ExtBuilder::try_state(false). This makes it possible for tests to leave broken staking state behind without noticing.

Task

Remove all usages of: ExtBuilder::default().try_state(false) from pallet-staking-async tests.

Tests that intentionally create invalid state should do one of:

• Assert that Staking::do_try_state(...) returns an error, then restore the state before the test ends.
• Use #[should_panic(expected = "...")] when the purpose of the test is to prove the post-test invariant check catches the bad state.

After all call sites are cleaned up, remove the try_state(false) builder API and the SkipTryStateCheck flag from the mock runtime.