Add test for list_nested_decimal

[ariesdevil]

Add test for list_nested_decimal, the data structure is:

[
    [[Decimal(0), Decimal(1)]],
    None,
    [[Decimal(2), None], [Decimal(3)]],
    [[Decimal(4), Decimal(5)], [Decimal(6)]],
    [],
    [[Decimal(7)], None, [Decimal(9)]],
    [[], [None], None],
    [[Decimal(10)]],
]

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (8880501) 83.06% compared to head (d46eabc) 83.05%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1572 +/- ## ========================================== - Coverage 83.06% 83.05% -0.01% ========================================== Files 391 391 Lines 42898 42898 ========================================== - Hits 35632 35631 -1 - Misses 7266 7267 +1 ``` [see 4 files with indirect coverage changes](https://app.codecov.io/gh/jorgecarleitao/arrow2/pull/1572/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jorge+Leitao)

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