Add benchmarks for bulk-replace operations against Boost or STL

[Ash Vardanian]

The C++ class implements a replace_all operation, that can be used to replace all occurrences of a substring or a character with a different string. The implementation is designed to minimize memory allocations and should be faster than boost::algorithm::replace_all in Boost and Python's str.replace. That intuition should be supported by evidence, so new benchmarks should be added.