Figure.plot3d: Deprecate parameter "color" to "fill" (remove in v0.12.0)

[seisman]

Description of proposed changes

Related to #1617.

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If wrapping a new module, open a 'Wrap new GMT module' issue and submit reasonably-sized PRs.
• If adding new functionality, add an example to docstrings or tutorials.

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[seisman]

Ping @GenericMappingTools/pygmt-maintainers for a final review because plot3d is widely used so the deprecation will affect many users.

[michaelgrund]

Also fine!

[weiji14]

Can we rename the PR title to "Figure.plot3d: Deprecate parameter "color" to "fill" (remove in v0.12.0)", since this is just a deprecation warning and not a full removal yet?