[SimplifyCFG] Enable branch predicate canonicalization by default

[yrouban]

Summary

The introduction of the branch predicate canonicalization in SimplifyCFG (D84491) might affect many users.
This patch allows a simple revert and further investigation for any found issues.

[kuhar]

Would it make sense to enable the canonicalization in SimplifyCFG and disable the one in InstCombine as a single patch?

[lebedev.ri]

Abandon now that D84763 has resolved the base problem?

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

 
 static cl::opt<int>
 MaxSmallBlockSize("simplifycfg-max-small-block-size", cl::Hidden, cl::init(10),
                   cl::desc("Max size of a block which is still considered "
                            "small enough to thread through"));
 
 static cl::opt<bool>
     CanonicalizeBranchPredicates("simplifycfg-canonicalize-branch-predicates",
-                                 cl::Hidden, cl::init(false),
+                                 cl::Hidden, cl::init(true),
                                  cl::desc("Canonicalize branch predicates"));
 
 STATISTIC(NumBitMaps, "Number of switch instructions turned into bitmaps");
 STATISTIC(NumLinearMaps,
           "Number of switch instructions turned into linear mapping");
 STATISTIC(NumLookupTables,
           "Number of switch instructions turned into lookup tables");
 STATISTIC(