LibWeb: Implement "Determine the type of a calculation" algorithm

This is sitting alongside our old implementation for the moment.

Author: AtkinsSJ

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -8770,6 +8770,7 @@ class UnparsedCalculationNode final : public CalculationNode {
 
     virtual ErrorOr<String> to_string() const override { VERIFY_NOT_REACHED(); }
     virtual Optional<CalculatedStyleValue::ResolvedType> resolved_type() const override { VERIFY_NOT_REACHED(); }
+    virtual Optional<CSSNumericType> determine_type(Web::CSS::PropertyID) const override { VERIFY_NOT_REACHED(); }
     virtual bool contains_percentage() const override { VERIFY_NOT_REACHED(); }
     virtual CalculatedStyleValue::CalculationResult resolve(Optional<Length::ResolutionContext const&>, CalculatedStyleValue::PercentageBasis const&) const override { VERIFY_NOT_REACHED(); }