Consolidate duplicate implementations of max subarray

[tianyizheng02]

Describe your change:

Fixes #8812

• For the implementation of the dynamic programming algorithm for max subarray sum, I deleted maths/kadanes.py, maths/largest_subarray_sum.py, and other/maximum_subarray.py in favor of dynamic_programming/max_sum_contiguous_subsequence.py, which I renamed to max_subarray_sum.py.
• For the implementation of the divide-and-conquer algorithm, I deleted divide_and_conquer/max_subarray_sum.py in favor of divide_and_conquer/max_sub_array.py, which I renamed to divide_and_conquer/max_subarray.py.
• Added type hints and doctests to both implementations, with most of the tests having been taken from the deleted implementations.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".