Cannot retrieve 'qid' field from DMatrix

It doesn't seem to be possible to retrieve the 'qid' field of a DMatrix, neither as an integer field, nor as a float field.

Example:
```python
import numpy as np, xgboost as xgb
rng = np.random.default_rng(seed=13)
X = rng.standard_normal(size=(100,10))
y = rng.integers(1, size=100)
qid = rng.integers(3, size=100)
qid = qid[np.argsort(qid)]
dm = xgb.DMatrix(X, label=y, qid=qid)
```
```python
dm.get_uint_info("qid")
```
```
XGBoostError: [20:23:13] [/workspace/src/data/data.cc:628](https://untitled+.vscode-resource.vscode-cdn.net/workspace/src/data/data.cc:628): Unknown uint32 field name: qid
```
```python
dm.get_float_info("qid")
```
```
XGBoostError: [20:23:26] [/workspace/src/data/data.cc:619](https://untitled+.vscode-resource.vscode-cdn.net/workspace/src/data/data.cc:619): Unknown float field name: qid
```

Since one can get the group when supplying `qid`, I guess it should be possible to retrieve `qid` too.