Client API: Apply siblings on retrieved tags

[walramb]

For some use cases I want a "normalized" tag list where it applies siblings like it does in the main tag sidebar, but right now the API only returns the literal stored tags.

My use cases mostly involve counting and comparing tags between different files where I, for example, don't want female and gender:female to be counted separately.

I imagine this would either be a boolean argument on GET /get_files/file_metadata to have it apply siblings before sending,
or a command similar to GET /add_tags/clean_tags where you can pass in a batch of tags, this would be more flexible but probably slow since it needs a lot more back-and-forth through the API.

[floogulinc]

This would also be nice for Hydrus Web to be able to display the same tags the client does.

[floogulinc]

Added in https://github.com/hydrusnetwork/hydrus/releases/tag/v419