Fix timestamps and system notes when cloning issues

What does this MR do and why?

Our docs say:

Does not copy comments or system notes unless --with_notes is provided as an argument.

But we actually copy resource events which are rendered as system notes. This fixes that bug so that only system notes related to cloned attributes will be generated.

This also changes the cloned issue's created_at so that it is set to the time of clone.

Related to #362546 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Use the /clone quick action on an issue
2. Check the timestamps and system notes on the new issue

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #362546 (closed)