Add helpful hint error message if optional dependencies not yet installed.

[Sevans711]

Addresses part of #1224 #1225 but does not fully close them.

Overview

Adds _raise_hint_if_optional_deps_missing which raises helpful hint upon trying but failing to import optional dependencies due to them not yet being installed.

PR Checklist

General

• An issue is created and linked
• Added appropriate labels (if your uxarray repo permissions allow it)
• Filled out Overview and Expected Usage (if applicable) sections

Testing & Benchmarking

• Adequate tests are created if there is new functionality
• Tests are not too basic (such as simply calling a function and nothing else)
• Tests cover all major paths in your new functions
• [N/A] If this PR could affect performance, ran ASV benchmarks and confirmed they show expected behavior (add a new benchmark if necessary)

Documentation

• Docstrings have been added to all new functions
• Docstrings have been updated with any function changes
• [N/A] User (public) functions have been added to docs/api.rst
• Internal (private) function names start with an underscore (_)

AI Disclosure

AI Usage: GitHub Copilot inline code suggestions, some discussion with Claude.

• I take responsibility for all AI-generated content in my PR.
• I have tested all AI-generated content in my PR.