[clang-tidy] Include std::basic_string_view in readability-redundant-string-init.

std::string_view("") produces a string_view instance that compares
equal to std::string_view(), but requires more complex initialization
(storing the address of the string literal, rather than zeroing).

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D91009