Research conditionalising of autoonboarding of new Fedora packages for opt-out

[lbarcziova]

Followup of https://fedoraproject.org/wiki/Changes/AutomatedPackitOnboarding, where the decision was:

AGREED: The proposal is approved with the modification that it's just opt-in for F42. Switching to opt-out can be proposed for F43 (+9, 0, 0)
INFO: FESCo also requests that the Packit team investigate conditionalizing for known problematic packages such as rust-* to be excluded from future opt-out.

This should be done before #2695.

The task here is to research conditionalising for known problematic packages such as rust-* from the proposed future opt-out.