This patch changes how the SMT bug refutation runs in an equivalent bug report class.
Now, all other visitor are executed until they find a valid bug or mark all bugs as invalid. When the one valid bug is found (and crosscheck is enabled), the SMT refutation checks the satisfiability of this single bug.
If the bug is still valid after checking with Z3, it is returned and a bug report is created. If the bug is found to be invalid, the next bug report in the equivalent class goes through the same process, until we find a valid bug or all bugs are marked as invalid.
Massive speedups when verifying redis/src/rax.c, from 1500s to 10s.