Modify add_column() to optionally accept a FeatureType as param
Fix #7142.

**Before (Add + Cast)**:

```
from datasets import load_dataset, Value
ds = load_dataset("rotten_tomatoes", split="test")
lst = [i for i in range(len(ds))]

ds = ds.add_column("new_col", lst)
# Assigns int64 to new_col by default
print(ds.features)

ds = ds.cast_column("new_col", Value(dtype="uint16", id=None))
print(ds.features)
```


**Before (Numpy Workaround)**:

```
from datasets import load_dataset
import numpy as np
ds = load_dataset("rotten_tomatoes", split="test")
lst = [i for i in range(len(ds))]

ds = ds.add_column("new_col", np.array(lst, dtype=np.uint16))
print(ds.features)
```

**After**:
```
from datasets import load_dataset, Value
ds = load_dataset("rotten_tomatoes", split="test")
lst = [i for i in range(len(ds))]
val = Value(dtype="uint16", id=None))
ds = ds.add_column("new_col", lst, feature=val)
print(ds.features)
```