fix(rust,python): updated Display trait for enum categoricals

[alexander-beedie]

Closes #13330.

Updated DataType::Display trait for enum categoricals.

Example

import polars as pl
compass_points = ["North", "East", "South", "West"]

df = pl.DataFrame(
    data = {"directions": compass_points},
    schema_overrides = {"directions": pl.Enum(compass_points)},
)
print( df )
# shape: (4, 1)
# ┌────────────┐
# │ directions │
# │ ---        │
# │ enum       │  << previously showed 'cat'
# ╞════════════╡
# │ North      │
# │ East       │
# │ South      │
# │ West       │
# └────────────┘

[stinodego]

Good call - just one comment on the implementation!