fix(ReCraft-API-node): allow custom multipart parser to return FormData

[bigcat88]

Follow up the bug found during developing new pylint rules: #10213

Currently all ReCraft nodes that accepts at the same time input file and RecRaft Control broken.

This happened cause aiohttp library does not expands list values in data= into repeated form fields, e.g.:

controls[colors][][rgb][]=40
controls[colors][][rgb][]=12
controls[colors][][rgb][]=3

The switch to aiohttp (to make node async) broke those nodes, cause aihttp serializes them as strings:

controls[colors][][rgb][]= "[40, 12, 3]"

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To prevent the fix from affecting all nodes again, I propose simply extending the current feature of custom multipart_parser and allowing it to return FormData instead of dict.

This way, the fix only touches the custom multipart_parser of ReCraft API nodes and does not affect any other API nodes.

Before this PR:

After this PR:

[bigcat88]

+label: Core

[Kosinkadink]

looks good, merging