Update the instructions for testing pygmt install

[seisman]

Description of proposed changes

• Clean up unnecessary packages for testing. Only pytest, pytest-mpl and ipython are needed
• Add pygmt.print_clib_info() for testing

Fixes #

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 adding new functionality, add an example to docstrings or tutorials.

[weiji14]

Haven't had time to test this locally but should be fine 🤞. Should supplement/replace pygmt.print_clib_versions() with pygmt.show_versions() once #460 is resolved.