Adds "Sort all Children" perf test

Adds a new perf tests: "sortAllChildren"

Signed-off-by: Ricardo Quesada <ricardoquesada@gmail.com>
Uses std::sort()

Uses std::sort() for inserting the nodes.

This code is not final, but preliminary results show that std::sort() is 60% faster

Signed-off-by: Ricardo Quesada <ricardoquesada@gmail.com>
Adds missing include
Merge pull request #3475 from ricardoquesada/perf_fixes

Adds "Sort all Children" perf test