Use version-unique filename for downloads

[alterNERDtive]

🗣 Description

Filenames should be unique to their Foundry version so we can download multiple versions in parallel on multiple instances using the same cache folder (see #1399).

Depends on #1409, but apparently stacked PRs are not supported across repositories yet?

💭 Motivation and context

Downloads always go into downloading.zip, then get renamed.

If you have more than a single version of Foundry downloading at the same time, you will end up with the wrong file. E.g. I had a 12.343 and a 13.351 starting up; the v13 got the short end of the straw, and I ended up with a 12.343 zip labeled as 13.351.

This should be solved by version-unique temporary file names.

🧪 Testing

I haven’t tested this yet, just getting the drafts done before I have to head out.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Add a tag or create a release.