Add globbing to workspace.exclude list

[Zagitta]

Motivation

Hello, I've added the ability to use globs in workspace.exclude to facilitate easier usage of git submodules as dependencies.

A common way of using git submodules is to have them all under a subfolder like repos or third-party and it would be nice to be able to just add new submodules without having to change the workspace.exclude list every time.

This small change allows the usage of globs in workspace.exclude just like it's allowed in workspace.members eg:

[workspace]
memebers = ["crates/*"]
exclude = ["repos/*"]

Implementation

The current implementation is not ideal as it just silently eats any globbing errors. However, in the interest of making the change as minimal as possible for the initial round of reviews, I deemed that acceptable.
If desired I can refactor the is_excluded function to return a CargoResult<bool> similar to what expand_member_path does for its glob handling.

Testing

I've added a test case to the testsuite called excluded_glob which should cover most cases but I'm open to hear if I missed any edge cases.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @weihanglo (or someone else) soon.

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[ehuss]

There is a broader discussion going on about the format that the workspace members/exclude fields should be using, and whether or not they should possibly be using gitignore-style patterns. I think it would be good to have a plan on how it should work before making changes here. There's more context in #4593, #6009 (comment), #6745, and #11362.

[weihanglo]

Thanks for the pull request!

I am going to close this. Further discussion could happen in #11405. If we reach a consensus on supporting glob in workspace.exclud this could be revived :)