Rollup merge of #141936 - WaffleLapkin:report-in-deps-decoupling, r=oli-obk

Decouple "reporting in deps" from `FutureIncompatibilityReason`

The reason should just be it -- the reason. It never felt right to me that it was also responsible for whatever we include the warning in cargo's reports.

It gets especially unruly if you want to add non-`FutureReleaseError*` warnings which are included in the reports.

I just added a field to `FutureIncompatibleInfo` to control whatever the diagnostic is included in the cargo's reports.

Author: matthiaskrgr