Hide storage path for merge collections (#3902)

#### 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
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

* #3895

#### Test Plan

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

src/internal/kopia/merge_collection.go

@@ -70,7 +70,9 @@ func (mc *mergeCollection) Items(
 		for _, c := range mc.cols {
 			// Unfortunately doesn't seem to be a way right now to see if the
 			// iteration failed and we should be exiting early.
-			ictx := clues.Add(ctx, "merged_collection_storage_path", c.storagePath)
+			ictx := clues.Add(
+				ctx,
+				"merged_collection_storage_path", path.LoggableDir(c.storagePath))
 			logger.Ctx(ictx).Debug("sending items from merged collection")
 
 			for item := range c.Items(ictx, errs) {
@@ -95,7 +97,9 @@ func (mc *mergeCollection) FetchItemByName(
 		"merged_collection_count", len(mc.cols))
 
 	for _, c := range mc.cols {
-		ictx := clues.Add(ctx, "merged_collection_storage_path", c.storagePath)
+		ictx := clues.Add(
+			ctx,
+			"merged_collection_storage_path", path.LoggableDir(c.storagePath))
 
 		logger.Ctx(ictx).Debug("looking for item in merged collection")