Use mapAnyOf() and matchers based on it.
Use of binaryOperation() means that modernize-loop-convert and
readability-container-size-empty can now be used with rewritten binary
operators.
Differential Revision: https://reviews.llvm.org/D94131
This is how it should've been and brings it more in line with
std::string_view. There should be no functional change here.
This is mostly mechanical from a custom clang-tidy check, with a lot of
manual fixups. It uncovers a lot of minor inefficiencies.
This doesn't actually modify StringRef yet, I'll do that in a follow-up.