Add an `uninstall-all`/`clean` sub-command for xbuildenvs

[agriyakhetarpal]

One consequence of #148 is that the xbuildenvs are downloaded into the XDG cache or Library/Caches/ folder, which is not a convenient location for the end user to access. Multiple xbuildenvs can take up a bunch of space. For local development, the fact that we use a VCS-based versioning scheme means that I have a bunch of redundant xbuildenvs at any time on my machine per commit, which I need to go and either delete or uninstall one by one.

Thus, I would like to propose a command that removes them – as a wrapper over pyodide xbuildenv uninstall. We could call it:

• pyodide xbuildenv uninstall-all (similar to pipx, and closer in wording to uninstall which we already have); or
• pyodide xbuildenv clean (similar to uv cache clean or pip cache purge, as we're storing it in the caches directory)

I don't have a preference here, but I'm happy to hear opinions on either of the options.

[hoodmane]

the fact that we use a VCS-based versioning scheme

Could we also change this version less often? Or make a separate version that we only change when we change install_xbuildenv?

[hoodmane]

I think I like clean better.

[agriyakhetarpal]

the fact that we use a VCS-based versioning scheme

Could we also change this version less often? Or make a separate version that we only change when we change install_xbuildenv?

I'm unsure if I understood what you meant – the version changes on every commit, right? Do you suggest we compute the hexdigest or perhaps generate a UUID based on the contents of the CrossBuildEnvManager.install() function and use that to provision the version?

[hoodmane]

We could call the folder .pyodide-xbuildenv-1 and then rename it to .pyodide-xbuildenv-2 if we change CrossBuildEnvManager.install().

[agriyakhetarpal]

Ah, okay, that sounds good to me. That seems like the approach pytest takes for its testing folders, which are named pytest-of-username/test_run_number/, with the difference that it stores them in temporary directories and then discards them.