Add class properties to symbols outline

[Klaas058]

Currently class properties are not outlined and therefore not showing up in the symbol search in Zed

Test case:

<?php

class TestCase
{
    public $noType;
    protected string $withType = "default";
    private static array $static = [];
    protected readonly bool $readOnly;

    public function __construct(public bool $promotedProperty) {}
}

Before this change:

After this change:

Ideally promoted class properties would also work, but this is a start.

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[Klaas058]

@cla-bot check

[cla-bot]

We require contributors to sign our Contributor License Agreement, and we don't have @Klaas058 on file. You can sign our CLA at https://zed.dev/cla. Once you've signed, post a comment here that says '@cla-bot check'.

[cla-bot]

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[Klaas058]

@cla-bot check

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!