scripted-diff: Rename ValidAsCString to ContainsNoNUL

-BEGIN VERIFY SCRIPT-
 sed -i 's,ValidAsCString,ContainsNoNUL,g' $(git grep -l ValidAsCString)
-END VERIFY SCRIPT-

src/util/string.h

@@ -91,7 +91,7 @@ inline std::string MakeUnorderedList(const std::vector<std::string>& items)
 /**
  * Check if a string does not contain any embedded NUL (\0) characters
  */
-[[nodiscard]] inline bool ValidAsCString(std::string_view str) noexcept
+[[nodiscard]] inline bool ContainsNoNUL(std::string_view str) noexcept
 {
     for (auto c : str) {
         if (c == 0) return false;