chore(framework): Move and improve subscriber loader (#8347)

**What**
Move `SubscriberLoader` and improve implementation

FIXES FRMW-2635

integration-tests/modules/__tests__/event-bus/index.spec.ts

@@ -32,7 +32,7 @@ medusaIntegrationTestRunner({
         expect(testEventPayloadHandlerMock).toHaveBeenCalled()
         expect(
           testEventPayloadHandlerMock.mock.calls[0][0].pluginOptions
-        ).toEqual({})
+        ).toEqual(expect.any(Object))
         expect(testEventPayloadHandlerMock.mock.calls[0][0].event).toEqual({
           name: eventName,
           data: {

integration-tests/modules/package.json

@@ -5,7 +5,7 @@
   "license": "MIT",
   "private": true,
   "scripts": {
-    "test:integration": "NODE_OPTIONS=--experimental-vm-modules jest --silent=false --no-cache --maxWorkers=50% --bail --detectOpenHandles --forceExit --logHeapUsage",
+    "test:integration": "NODE_OPTIONS=--experimental-vm-modules jest --no-cache --maxWorkers=50% --bail --detectOpenHandles --forceExit --logHeapUsage",
     "test:integration:chunk": "NODE_OPTIONS=--experimental-vm-modules jest --silent --no-cache --bail --maxWorkers=50% --forceExit --testPathPattern=$(echo $CHUNKS | jq -r \".[${CHUNK}] | .[]\")",
     "build": "tsc --allowJs --outDir ./dist"
   },