Refactor and fix promise chain handling

[g105b]

This pull request includes changes to improve promise chain handling, addressing issues in finally and rejection resolutions. It also refactors code for better readability and reduces complexity by removing duplication.

Changes

• Fixed handling of finally within promise chains (New then chains should resolve with original resolution #75).
• Improved rejection handling to resolve chains with a static value (New then chains should resolve with original resolution #75).
• Fixed new issues in chain resolution, ensuring expected behavior (New then chains should resolve with original resolution #75).
• Added tests to validate exception handling when catch is not configured.
• Began tests for unhandled promise rejections.
• Simplified and refactored complex and duplicated code for maintainability.