Refactor to prepare for addressing shorthand property issues

Introduce a mechanism to auto-generate CSS property definitions in propertyDefinitions.js, and refactor the codebase to use these generated definitions. This will be used eventually in jsdom to replace propertiesWithResolvedValueImplemented in jsdom's lib/jsdom/living/helpers/style-rules.js, allowing jsdom to delegate property metadata management entirely to cssstyle.

Refactor normalize.js into smaller functions with clearer roles.

Replace string literals with constants where possible.

This work is mostly preparatory, but it does fix web-platform-tests/to-upstream/css/cssom/style-border-shorthand-var.html.

Follow-up work will implement the complex logic for expanding shorthands into longhands.

Author: asamuzaK

.gitignore

@@ -2,3 +2,4 @@ node_modules
 npm-debug.log
 lib/generated/implementedProperties.js
 lib/generated/properties.js
+lib/generated/propertyDefinitions.js

lib/CSSStyleDeclaration.js

@@ -10,7 +10,7 @@ const generatedProperties = require("./generated/properties");
 const {
   borderProperties,
   getPositionValue,
-  normalizeBorderProperties,
+  normalizeProperties,
   prepareBorderProperties,
   prepareProperties,
   shorthandProperties
@@ -150,7 +150,7 @@ class CSSStyleDeclaration {
       }
       properties.set(property, { property, value, priority });
     }
-    const normalizedProperties = normalizeBorderProperties(properties);
+    const normalizedProperties = normalizeProperties(properties);
     const parts = [];
     for (const { property, value, priority } of normalizedProperties.values()) {
       if (priority) {