[Bug] Convert opensearch-docker-entrypoint.sh script into python

[peternied]

Related #1529

Based on operation system configuration some command line utilities such as cat/sed/tee can have different behavior. In order to make the startup behavior consistent and testable lets move this script to python, which is included in the docker image already.

Acceptance Criteria:

• There should be no library python dependencies needed that would require an update the docker image.
• Create opensearch-docker-entrypoint.py that replaces the behavior of the existing entry point script
• Create tests for this file that are verified on pull request
• Make sure the pre-commit checks also apply to these files

[gaiksaya]

[Triage] We need to investigate the benefits of python over shell and vice versa.

[dblock]

I would prefer extracting much of what the code in shell scripts does into the product itself. For example, turning security on/off in the configuration file could become a command-line flag, etc.