Update Default Fallback Version for npm to npm8

[kbukum1]

What are you trying to accomplish?

This update changes the default fallback version for npm from npm 6 to npm 8. This adjustment aligns with our current support policy, where npm versions 7, 8, and 9 are supported, while npm 6 is not. The change improves compatibility for projects that lack explicit npm versioning in lockfiles, defaulting them to npm 8 for better dependency resolution.

What issues does this affect or fix?

• Resolves potential compatibility issues for projects using unsupported npm 6 by using npm 8 as the default fallback.
• Ensures npm 8 is the standard fallback in cases where lockfiles don’t specify npm 9 compatibility.

Anything you want to highlight for special attention from reviewers?

• The code now consolidates npm handling to supported versions (7, 8, and 9) with npm 8 as the fallback.
• Constants for npm, pnpm, and yarn versions have been created for easier updates and centralized control.

How will you know you've accomplished your goal?

• Testing: All tests pass, especially those involving npm version checks to ensure npm 8 is selected as the fallback where required.
• Validation: Successfully tested with projects that previously relied on npm 6, demonstrating expected behavior with npm 8 as the fallback.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.

[kbukum1]

Branch name is changed: #10755