feat: NDarray/Tensor support

[ritchie46]

On the 1.0 release we will

• change the constructor of Series to read 2D arrays to Array type instead of List.
• Default reshape to Array instead of List.

Higher dimensions will now go to Array with a multidimensional shape instead of Object.

Constructors coming

>>> pl.Series(range(64)).reshape((4, 2, 1, -1), nested_type=pl.Array)
shape: (4,)
Series: '' [array[i64, shape: (2, 1, 8)]]
[
    [[[0, 1, … 7]], [[8, 9, … 15]]]
    [[[16, 17, … 23]], [[24, 25, … 31]]]
    [[[32, 33, … 39]], [[40, 41, … 47]]]
    [[[48, 49, … 55]], [[56, 57, … 63]]]
]

[codecov]

Codecov Report

Attention: Patch coverage is 69.31217% with 58 lines in your changes are missing coverage. Please review.

Project coverage is 81.43%. Comparing base (717277e) to head (46545fa).
Report is 15 commits behind head on main.

Files	Patch %	Lines
crates/polars-ops/src/series/ops/reshape.rs	58.53%	34 Missing ⚠️
crates/polars-plan/src/dsl/function_expr/schema.rs	37.50%	5 Missing ⚠️
crates/polars-core/src/datatypes/dtype.rs	84.61%	4 Missing ⚠️
py-polars/polars/datatypes/classes.py	82.60%	2 Missing and 2 partials ⚠️
crates/polars-plan/src/dsl/function_expr/mod.rs	25.00%	3 Missing ⚠️
...lars/polars/testing/parametric/strategies/dtype.py	50.00%	2 Missing ⚠️
crates/polars-expr/src/expressions/mod.rs	0.00%	1 Missing ⚠️
...ates/polars-plan/src/dsl/function_expr/dispatch.rs	75.00%	1 Missing ⚠️
crates/polars-plan/src/dsl/function_expr/list.rs	50.00%	1 Missing ⚠️
crates/polars-plan/src/dsl/options.rs	0.00%	1 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16466      +/-   ##
==========================================
- Coverage   81.45%   81.43%   -0.03%     
==========================================
  Files        1409     1409              
  Lines      184713   184946     +233     
  Branches     2971     2978       +7     
==========================================
+ Hits       150467   150614     +147     
- Misses      33726    33811      +85     
- Partials      520      521       +1     

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[ritchie46]

We definitely don't want to go through the engine during construction. So added reshape directly on Series.

[ritchie46]

This branch still returns List<i64> for 2D arrays. Will remove that during 1.0, so we return an Array type here.