Show bot instance ID in tbot log output (#44578)

This tweaks the "fetched new bot identity" message to show the bot
name and instance ID as embedded in the bot's certificate.

Example:

```
2024-07-23T15:51:20-06:00 INFO [TBOT:IDEN] Fetched new bot identity identity:tpm-test, id=5a2865d3-d3dc-4eaa-853c-5377a1fe83f6 | valid: after=2024-07-23T21:50:20Z, before=2024-07-23T21:56:19Z, duration=5m59s | kind=tls, renewable=false, disallow-reissue=false, roles=[bot-tpm-test], principals=[-teleport-internal-join], generation=0 tbot/service_bot_identity.go:223
```

lib/tbot/output_utils.go

@@ -276,9 +276,16 @@ func describeTLSIdentity(ctx context.Context, log *slog.Logger, ident *identity.
 		}
 	}
 
+	botDesc := ""
+	if tlsIdent.BotInstanceID != "" {
+		botDesc = fmt.Sprintf(", id=%s", tlsIdent.BotInstanceID)
+	}
+
 	duration := cert.NotAfter.Sub(cert.NotBefore)
 	return fmt.Sprintf(
-		"valid: after=%v, before=%v, duration=%s | kind=tls, renewable=%v, disallow-reissue=%v, roles=%v, principals=%v, generation=%v",
+		"%s%s | valid: after=%v, before=%v, duration=%s | kind=tls, renewable=%v, disallow-reissue=%v, roles=%v, principals=%v, generation=%v",
+		tlsIdent.BotName,
+		botDesc,
 		cert.NotBefore.Format(time.RFC3339),
 		cert.NotAfter.Format(time.RFC3339),
 		duration,