Add syntactic support for primary constructors

[thekid]

See https://wiki.php.net/rfc/primary-constructors and php/php-src#22510.

Implementation status

• class T([params])
• class T([params]) extends Base([arguments]) and forwarding, see here
• Declaration order

Requires no change to the XP Compiler, this is all handled syntactically.

See also

• Additional tests in XP Compiler @ Support primary constructors compiler#193
• This is similar to https://github.com/xp-lang/xp-records, which has primary construcotrs but uses a special recoed keywords.
• Kotlin: https://kotlinlang.org/docs/classes.html#secondary-constructors
• C# 12: https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/instance-constructors#primary-constructors
• Dart: https://dart.dev/language/primary-constructors