feat: add actions/cache version validation

[erikburt]

Changes

1. Refactoring ValidationCheck
   • Change the interface from ValidateFile to ValidateLine
   • The added complexity of validating the files separately, and having to combine the results afterwards was unnecessary.
   • Change all the implementations so it can validate each line as needed, and immediately combining the messages
2. Refactoring/Reorganizing validation
   • To support the above changes, and consolidate logic. Created a new validate.ts file that handles the general validation logic
3. Refactoring/Reorganizing file parsing
   • The file parsing logic was all over the place. I've now modified it to live in a single file.
   • By default, it now parses the diff and all existing files
     • This lets us annotate on existing problems, we are no longer limited to errors in the diff
     • To minimize spam all existing validators only operate on line changes
4. Add actions/cache version validation
   • This will validate that references to actions/cache are up-to-date, and will comment on the PR if the repo contains references.
   • Add toggle for this
5. More test coverage

Testing

• https://github.com/smartcontractkit/releng-test/actions/runs/13001921649?pr=61
• https://github.com/smartcontractkit/releng-test/pull/61/files
  • new outdated references causes an error and annotation
  • existing outdated references causes a warning and annotation

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RE-3330