Fail operation if we failed to fetch item data (#2199)

## Description

If GraphConnector reported errors while trying to fetch item data, fail the entire operation. This stops silent failures, but is a big hammer at the moment because there's no checks for items no longer being available.

Error reporting is minimal as well, but some info should be in the log.

**This effectively disables best-effort as any failure will result in the operation being reported as failed**

## Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No 

## Type of change

- [ ] 🌻 Feature
- [x] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

## Issue(s)

* #2196

## Test Plan

- [x] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

src/internal/operations/backup.go

@@ -205,10 +205,21 @@ func (op *BackupOperation) Run(ctx context.Context) (err error) {
 		return opStats.writeErr
 	}
 
+	opStats.gc = gc.AwaitStatus()
+
+	if opStats.gc.ErrorCount > 0 {
+		opStats.writeErr = multierror.Append(nil, opStats.writeErr, errors.Errorf(
+			"%v errors reported while fetching item data",
+			opStats.gc.ErrorCount,
+		)).ErrorOrNil()
+
+		// Need to exit before we set started to true else we'll report no errors.
+		return opStats.writeErr
+	}
+
 	// should always be 1, since backups are 1:1 with resourceOwners.
 	opStats.resourceCount = 1
 	opStats.started = true
-	opStats.gc = gc.AwaitStatus()
 
 	return err
 }