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

.changeset/config.json

@@ -7,7 +7,7 @@
   "access": "public",
   "baseBranch": "master",
   "updateInternalDependencies": "patch",
-  "ignore": ["integration-tests-api", "integration-tests-plugins"],
+  "ignore": ["integration-tests-api", "integration-tests-plugins", "integration-tests-repositories"],
   "snapshot": {
     "useCalculatedVersion": true
   }