Add stateless closure cache

[iluuu1994]

https://wiki.php.net/rfc/closure-optimizations#stateless_closure_caching

Extracted from #19941. Sadly, @DanielEScherzer discovered an edge-case I did not consider:

https://3v4l.org/uovSF#v8.5.9

class Foo {
    public function instanceCall() {
        return $this;
    }
    
    public function test($c) {
        return array_map($c, [1]);
    }
}

$foo = new Foo();
var_dump($foo->test('Foo::instanceCall'));

Here, the internal function array_map() can perform instance calls with just a named closure. Same with ['Foo', 'instanceCall']. That's quite esoteric, but this behavior should first be deprecated and removed before assuming it isn't being used.

So, for the time being, let's merge only the latter half of the RFC. Code bases with static properly annotated will still get the full performance benefit.