[Validator] Ensure that the parameter source URLs are used in the Podfile

Didn't work before because `instance_eval` changes the scope of the block
[Outdated] Refine pod outdated to show what pod update would do
[Outdated] Use the Analyzer to resolve the unpinned pods
[Outdated] Update for release CocoaPods version
Merge pull request #2501 from CocoaPods/feature/outdated

[Outdated] Refine pod outdated to show what pod update would do