Everywhere: Replace single-char StringView op. arguments with chars

This prevents us from needing a sv suffix, and potentially reduces the
need to run generic code for a single character (as contains,
starts_with, ends_with etc. for a char will be just a length and
equality check).

No functional changes.

Meta/Lagom/Tools/CodeGenerators/LibWeb/WrapperGenerator/IDLParser.cpp

@@ -60,7 +60,7 @@ static String convert_enumeration_value_to_cpp_enum_member(String const& value,
         } else {
             auto non_alnum_string = lexer.consume_while([](auto c) { return !is_ascii_alphanumeric(c); });
             if (!non_alnum_string.is_empty())
-                builder.append("_");
+                builder.append('_');
         }
     }