Add validation tests for v4 and v3 cli-tool-feeds

After talking briefly with Naren, it seems like the tests that can add value are something like these.

1. Make sure the package links that are part of the updated cli-tool-feed are valid (i.e. they are available and downloadable) >> This is to ensure there is no human error while updating existing item-templates/project-templates
2. Make sure the cli-tool-feed structure follows a knowledge base model which means a new property can be added but we cannot delete a property from existing elements.
@soninaren

Locate the v3 and v4 cli-tool-feed definitions, including their item-templates and project-templates, and check for any existing feed validation tests or test entry points. Add coverage for downloadable package links and for preserving existing properties while allowing new ones, then run the relevant validation test suite.

Written by the indexing model from the issue text.