Add integrationFor validation to repo fix command

- Added integrationFor field to BackstagePackageJson type
- Created fixIntegrationFor validator that ensures:
  - Field is only used on module packages
  - Value is an array of strings
  - All entries are valid package names
- Added validator to the publish fixers list

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/cli-node/src/monorepo/PackageGraph.ts

@@ -91,6 +91,11 @@ export interface BackstagePackageJson {
      */
     pluginPackages?: string[];
 
+    /**
+     * Package names that this module provides integration for. When any of these packages are used, this module should be suggested as a related integration.
+     */
+    integrationFor?: string[];
+
     /**
      * The feature types exported from the package, indexed by path.
      */