Authorize upgrade tests for testnet runtimes + `execute_as_governance` refactor (#7656)

Relates to: https://github.com/paritytech/polkadot-sdk/issues/7541 
Relates to: https://github.com/paritytech/polkadot-sdk/issues/7566

This PR contains improved test cases that rely on the governance
location as preparation for AHM to capture the state as it is.
It introduces `execute_as_governance_call`, which can be configured with
various governance location setups instead of the hard-coded
`Location::parent()`.

Additionally, it adds a test for `authorize_upgrade` to all SP testnets.


## TODO
- [x] rewrite all tests using
`RuntimeHelper::<Runtime>::execute_as_governance` (because it is using
hard-coded `Location::parent()`) to use
`RuntimeHelper::<Runtime>::execute_as_governance_call`

## Follow-up
- [ ] add similar test for westend-runtime
- [ ] add test that ensure xcm-executor adds `ClearOrigin` before all
side-effect sent to different chain

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Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>