Add regular RegExp Unicode property escape tests (#1014)

.../built-ins/RegExp/property-escapes/generated/Uppercase.js

...s/RegExp/property-escapes/generated/Variation_Selector.js

...uilt-ins/RegExp/property-escapes/generated/White_Space.js

...ilt-ins/RegExp/property-escapes/generated/XID_Continue.js

.../built-ins/RegExp/property-escapes/generated/XID_Start.js

test/built-ins/RegExp/property-escapes/grammar-extensions.js

test/built-ins/RegExp/property-escapes/loose-matching.js

...p/property-escapes/non-binary-properties-without-value.js

...lt-ins/RegExp/property-escapes/non-existent-properties.js

...s/RegExp/property-escapes/non-existent-property-values.js

.../RegExp/property-escapes/unsupported-binary-properties.js

...ilt-ins/RegExp/property-escapes/unsupported-properties.js