Include catalog dependency changes when checking for changed packages

[ecraig12345]

Issue

Supposing a repo defines catalog/catalogs in .yarnrc.yml, and then it changes in a branch, e.g.:

  catalog:
-   react: ^18.0.0
+   react: ^19.0.0

The catalog dependency in a package looks like this in package.json, and by design, the file itself doesn't change:

{
  "name": "@scope/foo",
  "dependencies": {
    "react": "catalog:"
  }
}

With the initial implementation of catalog support in beachball, catalog-dependent packages like @scope/foo would not be listed as changed when the dependency's catalog version changes.

Fix

This PR updates the getChangedPackages logic to use a new function getCatalogChangedPackages which checks for catalog diffs:

• If the repo defines catalogs and the file with the catalog definition has changed, it gets the catalog file content from the target branch and compares the catalog objects.
• If there are any changes, it checks all included packages to get the list of packages using those catalog dependencies.

Most of the other changes are refactoring to support passing the previously-retrieved list of changed files to getCatalogChangedPackages, so we can skip the extra git operation of retrieving the file from the target branch if we already know it didn't change (which is by far the most common case). Removing one git operation doesn't matter much in small repos, but becomes important in extremely large repos.