RFC: Adding Github Codeowners File about sig-testing

[Kadino]

I don't foresee security impliciations with adding a well-known public feature, but it makes sense to solicit a review from SIG-Security. This type of data should be safe, especially if it avoids including individual users and remains focused only on tracking SIG-level ownership. In that case, it would be appropriate to add an early-warning rule to prevent adding an alias that is not one of the SIG aliases, in part to prevent typo errors.

One major upside from Codeowners: in tools performing actions like automated root cause analysis, this ownership info enables logging a human-readable recommendation about where/how to reach out for support.

[AMZN-scspaldi]

I support this effort and think it should be done. I have no requests for changes to this RFC.

[Kadino]

The start of this RFC is in progress: o3de/o3de#8277

[Kadino]

Additional requirements will be handled in separate issues