Problem

At least 2 of the arguments passed to Figure.__init__ do not have matching get_{kwarg}/set_{kwarg} methods on Figure which makes using fig.set(...) inconsistent with what can be done via Figure(...).

xref #21549 which was motivated by this and includes an implementation of the solution (along with some additional refactoring).

Proposed solution

See #21549 for a majority of the implementation. cherry-picking commits from that branch and dropping the layout management refactoring is a very good start.

• use alias mechanism for size_inches -> figsize
• add get/set_subplotparams
• use alias mechanism from layout -> layout_engine
• tests!
• whats new entry

Labeling this as good first issue because it is limited scope and easy because there is an existing implementation. There will be a discussion of API consistency so I think familiarity with Matplotlib's explicit API would be very helpful.