Update merge_sort.py with new implementation #Fixes 8098

[csana004]

Describe your change:

Added a merge sort implementation in sorts/merge_sort.py. The implementation includes insertion, recursive and iterative approaches with proper doctests.

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 Concatenate/consolidate all algorithms with different implementations #8098".

[imSanko]

Need to fix this:

ruff check --output-format=github .
  shell: /usr/bin/bash -e {0}

[Pajriboy1]

Hi

[cclauss]

Closing tests_are_failing PRs to prepare for Hacktoberfest 2024