Print the point in time being used (#4032)

When looking for recently deleted backups, print the point in time that kopia will be opened at so that if we need to manually debug something the value is right there.

---

#### 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
- [x] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

* #4031

#### Test Plan

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

src/cmd/longevity_test/longevity.go

@@ -73,6 +73,12 @@ func pitrListBackups(
 	pitr time.Time,
 	backupIDs []string,
 ) error {
+	logAndPrint(
+		ctx,
+		"looking for %d backup(s) using timestamp %v\n",
+		len(backupIDs),
+		pitr)
+
 	if len(backupIDs) == 0 {
 		return nil
 	}