feat(attributes): add support for spanAttributes, which allows to capture values

[Litarnus]

Add support for the special attribute spanAttributes which allows the extension to capture parameters and add them to the metadata array.

For example:

function foo(string $name) { ... }

\Sentry\instrument(null, "foo", spanAttributes: ['description' => 'name']);

setEndCallback(static function(array $data) {
    $data['metadata']['description']; <- will contain "example", the value of $name
});

foo("example");

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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