CI: Disable runtime upgrade spec name check on Westend Asset Hub and fix Staking pallet migration (#2447)

Westend Asset Hub currently failing because the spec name is being
changed next runtime upgrade
(https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/4413125).

This also fixes an idempotency issue with a staking pallet migration.
Similar issues will be caught automatically now that we've also updated
to try-runtime-cli v0.5.0 which checks for idempotency issues.

This also enables try-state checks running in the CI.