ddb.ResolveTag latency results in timeouts on DoltHub

[ddb.ResolveTag](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/doltdb/doltdb.go#L580) is slow for DoltHub databases with a large number of tags.

Latency appears to come from:
```go
ds, err := ddb.db.GetDataset(ctx, tagRef.String())
if err != nil {
return nil, ErrTagNotFound
}
```

```go
dc, err := datas.LoadCommitAddr(ctx, vrw, commitAddr)
if err != nil {
return nil, err
}
```

```go
commit, err := NewCommit(ctx, vrw, ns, dc)
if err != nil {
return nil, err
}
```

each of which can have variable latency from 300-700ms.