[CI] Disallowed std::string_view (#37930)

`std::string_view` is not allowed to use per Google C++ style guide. This test will prevent us from accidentally using it after C++17 upgrade.

Closes #37930

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/37930 from veblush:string-view 88f56c12ba
PiperOrigin-RevId: 686526151

tools/run_tests/sanity/cpp_banned_constructs.sh

@@ -24,7 +24,7 @@ cd "$(dirname "$0")/../../.."
 #
 
 grep -EIrn \
-    'std::(mutex|condition_variable|lock_guard|unique_lock|thread)' \
+    '\bstd::(mutex|condition_variable|lock_guard|unique_lock|thread|string_view)' \
     include/grpc include/grpcpp src/core src/cpp | \
     grep -Ev 'include/grpcpp/impl/sync.h|src/core/util/work_serializer.cc' | \
     diff - /dev/null