Refactor: Replace whoami with id -u -n in scripts for POSIX compliance (#854)

[shuchitpant]

This PR addresses issue #854 by replacing all instances of the whoami command with id -u -n, aligning with the POSIX standard for guaranteed behavior across Unix-like systems.

Changes Made:

• Conducted a find-and-replace for whoami across relevant scripts and documentation files.
• Verified using grep that no remaining whoami instances exist within the repository.

This simple refactor improves cross-platform compatibility, following best practices as outlined in the issue description.

[coolaj86]

I edited the commit to remove some junk temporary files that were mistakenly committed. Other than that, great.

Thank you!