fix: fixes and improvements Update besu-entry.sh

[annwag]

PR description

I’ve made several updates to address issues and improve the script’s reliability, readability, and maintainability.

Here’s a summary of the changes:

1. Explicit Exit for Non-Root Users: Added exit 0 after exec to ensure the script terminates immediately, preventing unintended behavior.
2. Variable Validation: Added a check for BESU_USER_NAME to avoid errors from undefined variables.
3. Error Handling: Improved error handling for the besu --print-paths-and-exit command to fail early if the command fails.
4. Output Parsing: Replaced IFS=: with cut to correctly handle paths with spaces or special characters.
5. Quoted Variables: Wrapped variables in quotes to prevent issues with paths containing spaces or special characters.
6. Logging: Added echo statements for better debugging and progress tracking.
7. Readability: Added comments and restructured the code for clarity and easier maintenance.

Thanks for sending a pull request! Have you done the following?

• Checked out our contribution guidelines?
• Considered documentation and added the doc-change-required label to this PR if updates are required.
• Considered the changelog and included an update if required.
• For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests