Ensure outbound XCMs are decodable with limits + add `EnsureDecodableXcm`...

Ensure outbound XCMs are decodable with limits + add `EnsureDecodableXcm` router (for testing purposes) (#4186)

This PR:
- adds `EnsureDecodableXcm` (testing) router that attempts to *encode*
and *decode* passed XCM `message` to ensure that the receiving side will
be able to decode, at least with the same XCM version.
- fixes `pallet_xcm` / `pallet_xcm_benchmarks` assets data generation

Relates to investigation of
https://substrate.stackexchange.com/questions/11288 and missing fix
https://github.com/paritytech/polkadot-sdk/pull/2129 which did not get
into the fellows 1.1.X release.

## Questions/TODOs

- [x] fix XCM benchmarks, which produces undecodable data - new router
catched at least two cases
  - `BoundedVec exceeds its limit`
  - `Fungible asset of zero amount is not allowed`  
- [x] do we need to add `sort` to the `prepend_with` as we did for
reanchor [here](https://github.com/paritytech/polkadot-sdk/pull/2129)?
@serban300 (**created separate/follow-up PR**:
https://github.com/paritytech/polkadot-sdk/pull/4235)
- [x] We added decoding check to `XcmpQueue` -> `validate_xcm_nesting`,
why not to added to the `ParentAsUmp` or `ChildParachainRouter`?
@franciscoaguirre

 (**created separate/follow-up PR**:
https://github.com/paritytech/polkadot-sdk/pull/4236)
- [ ] `SendController::send_blob` replace `VersionedXcm::<()>::decode(`
with `VersionedXcm::<()>::decode_with_depth_limit(MAX_XCM_DECODE_DEPTH,
data)` ?

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Co-authored-by: Adrian Catangiu <[email protected]>