[CLI] Add support for --key.help=class

[carmocca]

What does this PR do?

Fixes #10725

This also requires jsonargparse>=4.0.4

Does your PR introduce any breaking changes? If yes, please list them.

None

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cc @Borda @carmocca @mauvilsa

[github-actions]

Build Error! No Linked Issue found. Please link an issue or mention it in the body using #<issue_id>

[tchaton]

LGTM ! Neat !

[mauvilsa]

jsonargparse 4.0.4 is now released.

[github-actions]

Build Error! No Linked Issue found. Please link an issue or mention it in the body using #<issue_id>