Only fetch a release URL if the requested version is not cached

[alterNERDtive]

🗣 Description

We do not have to fetch a release URL if the zip file for the requested Foundry version has already been cached (see #1399).

💭 Motivation and context

Currently, we are always fetching the release URL, no matter if we are actually going to use it or not. With multiple containers starting up at the same time, you immediately run into rate limiting on Foundry’s side.

🧪 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.