Revert rL349136: [llvm-exegesis] Optimize ToProcess in dbScan
Summary:
Use `vector<char> Added + vector<size_t> ToProcess` to replace `SetVector ToProcess`
We also check `Added[P]` to enqueueing a point more than once, which
also saves us a `ClusterIdForPoint_[Q].isUndef()` check.
Reviewers: courbet, RKSimon, gchatelet, john.brawn, lebedev.ri
Subscribers: tschuett, llvm-commits
Differential Revision: https://reviews.llvm.org/D54442
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Patch wasn't approved and breaks buildbots
llvm-svn: 349139