Meta+Userland: Simplify some formatters

These are mostly minor mistakes I've encountered while working on the
removal of StringView(char const*). The usage of builder.put_string over
Format<FormatString>::format is preferrable as it will avoid the
indirection altogether when there's no formatting to be done. Similarly,
there is no need to do format(builder, "{}", number) when
builder.put_u64(number) works equally well.

Additionally a few Strings where only constant strings were used are
replaced with StringViews.

Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateUnicodeDateTimeFormat.cpp

@@ -530,7 +530,7 @@ template<>
 struct AK::Formatter<Unicode::HourCycle> : Formatter<FormatString> {
     ErrorOr<void> format(FormatBuilder& builder, Unicode::HourCycle hour_cycle)
     {
-        return Formatter<FormatString>::format(builder, "{}", to_underlying(hour_cycle));
+        return builder.put_u64(to_underlying(hour_cycle));
     }
 };