[JENKINS-75003] Zip-based tool installer configuration incorrectly rejects non-HTTP(S) URLs (regression in 2.379)

[basil]

See JENKINS-75003. Amends #7398 to restore form validation support for non-HTTP(S) URLs.

Testing done

As described in the bug report, created a Maven tool with the "Extract *.zip/*.tar.gz" installer, using a download URL of file:///path/to/apache-maven-3.9.9-bin.tar.gz and a subdirectory of apache-maven-3.9.9. Verified that form validation failed before this PR and passed after this PR. Verified that a Pipeline job succeeded using this tool. Verified that a download URL of fil://path/to/invalid (invalid scheme) still reported a form validation error.

Proposed changelog entries

Allow non-HTTP(S) URLs in zip-based tool installer configuration (regression in 2.379).

Proposed upgrade guidelines

N/A

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[timja]

/label ready-for-merge

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This PR is now ready for merge, after ~24 hours, we will merge it if there's no negative feedback.

Thanks!