Remove `getAffectedRegisters` and `setOverwritingInstrs` methods from
the base `Report` class. Instead, rename the `Report` class to
`Diagnostic` and make it always represent the brief version of the
report, which is kept unchanged since initially found. Throughout its
life-cycle, an instance of `Diagnostic` is first wrapped into
`PartialReport<ReqT>` together with an optional request for extra
details. Then, on the second run of the analysis, it is re-wrapped into
`FinalReport` together with the requested detailed information.
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