[Clang][UnsafeBufferUsage] Warn about two-arg string_view constructors. (#180471)
"This patch extends the unsafe buffer usage warning to cover
std::string_view constructors that take a pointer and size, similar to
the existing check for std::span.
The warning message has been updated to be generic ('container
construction' instead of 'span construction') and existing tests have
been updated to match.
Fixes #166644."