Refactor eTag formatting logic into a static utility method

[hyunmin0317]

This pull request refactors the eTag formatting logic by consolidating it into a static format method within the ETag record class. The changes aim to eliminate duplicated code and improve maintainability.

Summary of Changes:

• Added a static format method to the ETag record class to handle eTag formatting.
• Refactored various classes to use the new format method for eTag formatting.

Thank you for reviewing this pull request!

[bclozel]

To be considered when we'll work on #33385