Allow loading modules without hashes

[shi-eric]

Description

These are some changes applied on top of the foundation set by #661 to take into account @mmacklin's suggestions and refactoring the tests in a way to be more robust:

• Rename disable_caching to force_cache_load (still unsure about the name)
• force_cache_load setting (global- or module-level)
• cache_dir setting (module-level only)

Before your PR is "Ready for review"

• [x] All commits are signed-off to indicate that your contribution adheres to the Developer Certificate of Origin requirements
• [x] Necessary tests have been added
• [x] Documentation is up-to-date
• [x] Auto-generated files modified by compiling Warp and building the documentation have been updated (e.g. stubs.py, functions.rst)
• [x] Code passes formatting and linting checks with pre-commit run -a

[shi-eric]

Hey @YuyangLee, this is what I'm currently planning for your features. Let me know if you have any suggestions to make it work well for your intended workflow.

Edit: Actually we're going back to the drawing board on this feature and rethinking the API. Will revisit when I get a chance, sorry.