GeneralizationStage takes an unreasonably long time

[addisoncrump]

While testing GeneralizationStage in libafl_libfuzzer, we observed that some inputs may take exceedingly long amounts of time to be generalized. This is due to two issues:

• [ ] GeneralizationStage cannot recover if a solution causes a crash or timeout, meaning that the fuzzer may never be able to complete a stage tuple execution for an input which has this behaviour (related: #1341)
• [ ] GeneralizationStage attempts to execute the input between every gap discovered in the input for whether it removes the most-recently-novel edges. This can mean tens of thousands of executions spent on generalization, only to squeeze out a few more inputs that might trigger new edges.

We should investigate if we can improve its performance or switch to other strategies (see: #1542).

[s1341]

I can confirm that this is still an issue!