Remove wrapping with extra msgpack array in stored procedure return values

Since https://github.com/tarantool/tarantool/issues/4799 is fixed, now we can use the compat.c_func_iproto_multireturn = 'new' option (introduced in this commit) which will make our rust stored procedure not add an extra msgpack array to the return values.

Current behaviour

This will make our "proc api" more friendly, e.g. .proc_version_info now can only return something like this:

[{"picodata_version": "23.12.1", "proc_api_version": "0.1.0"}]

or this

["23.12.1", "0.1.0"]

New behaviour

But after the fix we'll be able to return this:

{"picodata_version": "23.12.1", "proc_api_version": "0.1.0"}

Breaking compatibility

However this will be a breaking change and will require to fix code in many different places including sbroad.