LibWeb: Improve support for CalculatedStyleValue in translate

- Omit calcs that are resolved to `0px` from the serialized value
- Allow CSV to be the 'Z' component in interpolated value.
- Allow calcs with mixed percentages in the first two arguments.

To achieve the third item above the concept of a "special" value parsing
context has been added - this will also be useful for instance for
different arguments of color functions having different contexts.

Gains us 23 WPT tests

Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -1685,7 +1685,7 @@ bool Parser::context_allows_quirky_length() const
             [top_level_property](FunctionContext const& function_context) {
                 return function_context.name == "rect"sv && top_level_property == PropertyID::Clip;
             },
-            [](DescriptorContext const&) { return false; });
+            [](auto const&) { return false; });
     }
 
     return unitless_length_allowed;