Add emitting support for asymmetric visibility

[thekid]

This pull request adds emitting support for asymmetric visibility using (set) specifiers on property modifiers

• Rewrite private(set) and protected(set) to virtual properties
• Constructor parameter promotion
• Asymmetric visibility with readonly
• Reflection, depending on Add support for asymmetric visibility for properties reflection#43

See https://wiki.php.net/rfc/asymmetric-visibility-v2 and #182

[thekid]

Reflection

Here's a first idea:

$prop= $type->property('name');
$prop->modifiers();       // lang.reflection.Modifiers<public | private(set)>

$prop->modifiers('get');  // lang.reflection.Modifiers<public>
$prop->modifiers('set');  // lang.reflection.Modifiers<private>

[thekid]

Released in https://github.com/xp-framework/compiler/releases/tag/v9.2.0