feat(medusa): Extract cron job logic to its own service (#2821)

**What**
Extract cron job logic from the `EventBusService` to its own service `JobSchedulerService`

**Why**
Preliminary step to extracting the event bus into a module

**Tests**
Tested with a local installation of Medusa

Resolved CORE-918

packages/medusa-plugin-brightpearl/src/loaders/inventory.js

@@ -3,10 +3,10 @@ const inventorySync = async (container, options) => {
     return
   } else {
     const brightpearlService = container.resolve("brightpearlService")
-    const eventBus = container.resolve("eventBusService")
+    const jobSchedulerService = container.resolve("jobSchedulerService")
     try {
       const pattern = options.inventory_sync_cron
-      eventBus.createCronJob("inventory-sync", {}, pattern, () =>
+      jobSchedulerService.create("inventory-sync", {}, pattern, () =>
         brightpearlService.syncInventory()
       )
     } catch (err) {