pallet-xcm: Deprecate `execute` and `send` in favor of `execute_blob` and `send_blob` (#3749)

`execute` and `send` try to decode the xcm in the parameters before
reaching the filter line.
The new extrinsics decode only after the filter line.
These should be used instead of the old ones.

## TODO
- [x] Tests
- [x] Generate weights
- [x] Deprecation issue ->
https://github.com/paritytech/polkadot-sdk/issues/3771
- [x] PRDoc
- [x] Handle error in pallet-contracts

This would make writing XCMs in PJS Apps more difficult, but here's the
fix for that: https://github.com/polkadot-js/apps/pull/10350.
Already deployed! https://polkadot.js.org/apps/#/utilities/xcm

Supersedes https://github.com/paritytech/polkadot-sdk/pull/1798/

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Co-authored-by: PG Herveou <pgherveou@gmail.com>
Co-authored-by: command-bot <>
Co-authored-by: Adrian Catangiu <adrian@parity.io>