kv/kvserver: use proper formatting when debug printing intents

This commit changes the formatting used when printing intents via the
CLI debug command from the default generated Protobuf formatter to our
custom `MVCCMetadata` formatter implementation.  Additionally, the
`MergeTimestamp` and `TxnDidNotUpdateMetadata` fields have been added to
the output.  This changes the debug formatting from the former
example:
```
0,0 /Local/RangeID/203/r/RangePriorReadSummary (0x0169f6cb727270727300): {Txn:<nil> Timestamp:0,0 Deleted:false KeyBytes:0 ValBytes:0 RawBytes:[230 123 85 161 3 10 12 10 10 8 146 229 195 204 139 135 186 208 22 18 12 10 10 8 146 229 195 204 139 135 186 208 22] IntentHistory:[] Me
rgeTimestamp:<nil> TxnDidNotUpdateMeta:<nil>}
/Local/Lock/Intent/Table/56/1/1319/6/3055/0 0361fea07d3f0d40ba8f44dc4ee46cbdc2 (0x017a6b12c089f705278ef70bef880001000361fea07d3f0d40ba8f44dc4ee46cbdc212): 1630559399.176502568,0 {Txn:id=61fea07d key=/Table/57/1/1319/6/0 pri=0.01718258 epo=0 ts=1630559399.176502568,0 min=1630559399.176502568,0 seq=4 Timestamp:1630559399.176502568,0 Deleted:false KeyBytes:12 ValBytes:5 RawBytes:[] IntentHistory:[] MergeTimestamp:<nil> TxnDidNotUpdateMeta:0xc0016059b0}
```
to the following example:
```
0,0 /Local/RangeID/203/r/RangePriorReadSummary (0x0169f6cb727270727300): txn={<nil>} ts=0,0 del=false klen=0 vlen=0 raw=/BYTES/0x0a0c0a0a0892e5c3cc8b87bad016120c0a0a0892e5c3cc8b87bad016 mergeTs=<nil> txnDidNotUpdateMeta=false
/Local/Lock/Intent/Table/56/1/1319/6/3055/0 0361fea07d3f0d40ba8f44dc4ee46cbdc2 (0x017a6b12c089f705278ef70bef880001000361fea07d3f0d40ba8f44dc4ee46cbdc212): 1630559399.176502568,0 txn={id=61fea07d key=/Table/57/1/1319/6/0 pri=0.01718258 epo=0 ts=1630559399.176502568,0 min=1630559399.176502568,0 seq=4} ts=1630559399.176502568,0 del=false klen=12 vlen=5 mergeTs=<nil> txnDidNotUpdateMeta=true
```

Release justification: Bug fix
Release note: None

pkg/kv/kvserver/debug_print.go

@@ -103,7 +103,7 @@ func tryIntent(kv storage.MVCCKeyValue) (string, error) {
 	if err := protoutil.Unmarshal(kv.Value, &meta); err != nil {
 		return "", err
 	}
-	s := fmt.Sprintf("%+v", meta)
+	s := fmt.Sprintf("%+v", &meta)
 	if meta.Txn != nil {
 		s = meta.Txn.WriteTimestamp.String() + " " + s
 	}

pkg/storage/enginepb/mvcc.go

@@ -315,6 +315,12 @@ func (meta *MVCCMetadata) FormatW(buf io.Writer, expand bool) {
 			fmt.Fprintf(buf, " nih=%d", nih)
 		}
 	}
+
+	var txnDidNotUpdateMeta bool
+	if meta.TxnDidNotUpdateMeta != nil {
+		txnDidNotUpdateMeta = *meta.TxnDidNotUpdateMeta
+	}
+	fmt.Fprintf(buf, " mergeTs=%s txnDidNotUpdateMeta=%t", meta.MergeTimestamp, txnDidNotUpdateMeta)
 }
 
 func (meta *MVCCMetadataSubsetForMergeSerialization) String() string {