CI: Test on Windows arm64 runners

[weiji14]

Description of proposed changes

Because why not have more failing Windows tests 😆

References:

• https://github.blog/changelog/2025-04-14-windows-arm64-hosted-runners-now-available-in-public-preview/

Similar to #3778 but for Windows

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

[weiji14]

Getting an error on the setup-micromamba step at https://github.com/GenericMappingTools/pygmt/actions/runs/14458118336/job/40545485415?pr=3911:

Error: Unsupported platform: win32-arm64

I see that only win_arm64 as supported at https://github.com/mamba-org/mamba/blob/64a620a2aa046d7508a302a06d63f49425b48b7b/libmamba/include/mamba/specs/platform.hpp#L42 from mamba-org/mamba#2745. Maybe something needs to change on mamba, or the GitHub Actions runner. Edit: actually, probably need an extra entry here - https://github.com/mamba-org/setup-micromamba/blob/d17c2171caa36ec145ac7e4658406a66d9af236d/src/util.ts#L24-L31