refactor(medusa): move repository specs into its own folder (#2952)

**What:**

Introduces a new folder under which repository specs will be placed. 

Why:

We don't currently have a good place to test ORM logic or custom queries against the database. The repository folder tests are a place for just exactly that. 

How:

Creates an internal package similar to other integration tests - api and plugins. 

CORE-965

integration-tests/jest.config.js

@@ -14,6 +14,7 @@ module.exports = {
   projects: [
     "<rootDir>/integration-tests/api/jest.config.js",
     "<rootDir>/integration-tests/plugins/jest.config.js",
+    "<rootDir>/integration-tests/repositories/jest.config.js",
   ],
   testPathIgnorePatterns: [
     `/examples/`,