[xcm] runtime api for LocationToAccount conversions (#4857)

Closes: https://github.com/paritytech/polkadot-sdk/issues/4298

This PR also merges `xcm-fee-payment-runtime-api` module to the
`xcm-runtime-api`.


## TODO

- [x] rename `convert` to `convert_location` and add new one
`convert_account` (opposite direction)
- [x] add to the all testnet runtimes
- [x] check polkadot-js if supports that automatically or if needs to be
added manually https://github.com/polkadot-js/api/pull/5917
- [ ] backport/patch for fellows and release (asap)

## Open questions
- [x] should we merge `xcm-runtime-api` and
`xcm-fee-payment-runtime-api` to the one module `xcm-runtime-api` ?

## Usage
Input:
 - `location:  VersionedLocation`
 
Output:
 - account_id bytes


![image](https://github.com/paritytech/polkadot-sdk/assets/8159517/4607b15a-77d2-462b-806c-606107776c0d)

---------

Co-authored-by: Bastian Köcher <git@kchr.de>