fix: Raise informative error instead of panicking for list arithmetic on some invalid dtypes

[nameexhaustion]

Fixes #19839

We didn't validate that the list side of an arithmetic operation between list<->primitive columns has a list type at all nesting levels. This causes a panic when we later attempt to downcast to a numeric array type.

# Before
pyo3_runtime.PanicException: not implemented for dtype Struct([Field { name: "a", dtype: Int64 }])
# After
polars.exceptions.InvalidOperationError: cannot add columns: dtype was not list on all nesting levels: (left: list[struct[1]], right: i64)

Some drive-bys:

• Rename arithmetic/list_borrowed.rs -> arithmetic/list.rs (under polars-core)
• Rename arithmetic/test_list_arithmetic.py -> arithmetic/test_list.py (under py-polars/tests)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.37%. Comparing base (402c15e) to head (2292054).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #19841   +/-   ##
=======================================
  Coverage   79.37%   79.37%           
=======================================
  Files        1550     1550           
  Lines      214743   214763   +20     
  Branches     2460     2460           
=======================================
+ Hits       170457   170475   +18     
- Misses      43727    43729    +2     
  Partials      559      559           

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