fix(python): don't lose track of ones and zeros dtype, improve use with Array, raise error if dtype invalid

[alexander-beedie]

Various minor fixes/improvements to the ones and zeros convenience functions.
(Follow up from #13121 (comment)).

• Raise a suitable error on invalid/unsuitable "dtype" value instead of returning a series of null values.
• Ensure proper "dtype" pass-through from repeat → parse_as_list_of_expressions → lit.
• Extended test coverage to include error conditions, expected defaults, additional dtypes.
• Improve handling of Array dtype (get width and create 1/0 arrays of that length).

Examples

Improve handling of Array dtype:

pl.ones(n=2, dtype=pl.Array(pl.UInt8,width=3), eager=True)

Before

shape: (2,)
Series: 'ones' [null]
[
    null
    null
]

After

shape: (2,)
Series: 'ones' [array[u8, 3]]
[
   [1, 1, 1]
   [1, 1, 1]
]

Raise on unsuitable/invalid dtype:

pl.zeros(n=2, dtype=pl.Struct({"x": pl.Null, "y": pl.Duration}), eager=True) 

Before

shape: (2,)
Series: 'zeros' [struct[2]]
[
    {null,null}
    {null,null}
]

After

TypeError: invalid dtype for `zeros`; found Struct({'x': Null, 'y': Duration}))

[alexander-beedie]

(Rebased to pick up #13327 fix for Array dtype).