WIP: Figure.colorbar: Refactor using the new alias system

[seisman]

Description of proposed changes

Fixes #

Preview:

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.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash command is:

• /format: automatically format and lint the code

[yvonnefroehlich]

I feel it would be good to add an alias for -S,

-S[+aangle][+c|n][+r][+s][+xlabel][+yunit]

as I realized that this flags allows to set x and y labels in case frame (-B) cannot be used, e.g., if equalsize (-L) is used.
I am wondering if adding an alias, e.g., `appearance``, using the old alias system still makes sense or if we should do this directly using the new alias system to introduce aliases for the single modifieres.