fix: Make Array arithmetic ops fully elementwise

[coastalwhite]

Fixes #19679.

Along side two other issues.

Issue 1:

import polars as pl

a = pl.Series('a', [[[1, 2, 3], [4, 5, 6]]], pl.Array(pl.Int64, (2, 3)))

print(a + pl.Series([1]))
print(pl.Series([1]) + a)

shape: (1,)
Series: 'a' [array[i64, (2, 3)]]
[
    [[2, 3, 4], [5, 6, 7]]
]
Traceback (most recent call last):
  File "/home/johndoe/Projects/polars/array_elementwise_bug.py", line 6, in <module>
    print(pl.Series([1]) + a)
          ~~~~~~~~~~~~~~~^~~
  File "/home/johndoe/Projects/polars/py-polars/polars/series/series.py", line 1045, in __add__
    return self._arithmetic(other, "add", "add_<>")
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/johndoe/Projects/polars/py-polars/polars/series/series.py", line 994, in _arithmetic
    return self._from_pyseries(getattr(self._s, op_s)(other._s))
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
polars.exceptions.InvalidOperationError: add operation not supported for dtypes `i64` and `array[i64, (2, 3)]`

Issue 2:

import polars as pl

a = pl.Series('a', [[[1, 2, 3], [4, 5, 6]]], pl.Array(pl.Int64, (2, 3)))
print(a + a)

shape: (3,)
Series: 'a' [array[i64, 2]]
[
    [2, 4]
    [6, 8]
    [10, 12]
]

[codecov]

Codecov Report

Attention: Patch coverage is 77.64706% with 19 lines in your changes missing coverage. Please review.

Project coverage is 79.71%. Comparing base (4b03406) to head (48f044a).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
...ates/polars-core/src/series/arithmetic/borrowed.rs	75.64%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19682      +/-   ##
==========================================
- Coverage   79.73%   79.71%   -0.03%     
==========================================
  Files        1541     1542       +1     
  Lines      212227   212207      -20     
  Branches     2449     2449              
==========================================
- Hits       169226   169167      -59     
- Misses      42446    42485      +39     
  Partials      555      555              

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