Add json_serialize_plan, json_serialize_sql tweaks

[Maxxen]

This PR adds a new json_serialize_plan(VARCHAR) scalar function to serialize a sequence of semicolon-separated sql statements into a json containing a list of each statements query plan, in json format. This is now possible for most* operators due to the recent serialization overhaul.

Like the json_serialize_sql function, this also takes skip_empty := bool, skip_null := bool, format := bool optional arguments to control the json output, as well as an additional optimize := bool argument specifying whether or not to serialize after or before plan optimization (default false, without optimizing).

Future work:

• Implement de/serialization support for the last couple of unsupported operators
• Implement a way to execute the produced json serialized plans, similar to the json_execute_serialized_sql table function. This is more complicated since the plans are already bound after deserialization and some plans don't produce any values as results (e.g. insert), but we still need to bind some column return types/names if we go the table function route.

[Maxxen]

Great, the temp catalog name differs when running with --force-storage

[Mytherin]

Thanks!