FlattenSequence/distance(from:to:) benchmarks (v2).

1. Registered the new benchmarks in benchmark/utils/main.swift.

Author: oscbyspro

benchmark/utils/main.swift

@@ -283,6 +283,7 @@ register(Exclusivity.benchmarks)
 register(ExistentialPerformance.benchmarks)
 register(Fibonacci.benchmarks)
 register(FindStringNaive.benchmarks)
+register(FlattenDistanceFromTo.benchmarks)
 register(FlattenList.benchmarks)
 register(FloatingPointConversion.benchmarks)
 register(FloatingPointParsing.benchmarks)