contracts: Add RPC that allows instantiating of a contract (#8451)

* contracts: Add RPC that allows instantiating of a contract

* Encode `debug_message` as bytes because usage of `String` is forbidden

* Remove erroneous derive attribute

* Fix rpc tests for new `debug_message` encoding

* Fix typo

Co-authored-by: Andrew Jones <[email protected]>

Co-authored-by: Andrew Jones <[email protected]>