Use system clipboard for hitobjects in the editor

[minetoblend]

• Depends on Add support for custom clipboard formats osu-framework#6223

Uses the system clipboard when copy-pasting hitobjects in the editor. When copying hitobjects, 2 clipboard entries will be created:

• text/plain: contains the timestamp
• osu/hitobjects: contains the json-serialized version of the copied hitobjects

This allows copy-pasting objects between osu and external tools.

2024-03-24.02-04-50.mp4

[bdach]

aside from the framework prereq

[bdach]

not a valid mime format, should probably be something like application/x-osu-hitobjects

[Susko3]

https://www.rfc-editor.org/rfc/rfc6838.html#section-3.4

Subtype names with "x." as the first facet may be used for types
intended exclusively for use in private, local environments.

https://www.rfc-editor.org/rfc/rfc6838.html#section-4.2.8

Since this was published, the de facto practice has arisen for using
this suffix convention for other well-known structuring syntaxes. In
particular, media types have been registered with suffixes such as
"+der", "+fastinfoset", and "+json". This specification formalizes
this practice and sets up a registry for structured type name
suffixes.

So it should be application/x.osu.hitobjects+json.

Please note that web custom formats are prefixed with web in the javascript API (an image/png and web image/png can be different things). I'm still thinking about how this should be handled.