Set v8::Signature on FunctionTemplates

This causes v8 to verify the receiver of a function, and prevents calling an
accessor or function with the wrong receiver, e.g.:

```
const g = Object.getOwnPropertyDescriptor(Window.prototype, 'document').get;
g.call(null);
```

A few other cleanups in this commit:
1 - Define any accessor with a getter as ReadOnly
2 - Ability to define an accessor with the DontDelete attribute
    (window.document and window.location)
3 - Replace v8__ObjectTemplate__SetAccessorProperty__DEFAULTX overloads with
    new v8__ObjectTemplate__SetAccessorProperty__Config
4 - Remove unnecessary @constCast for FunctionTemplate which can be const
    everywhere.

build.zig.zon

@@ -5,8 +5,8 @@
     .minimum_zig_version = "0.15.2",
     .dependencies = .{
         .v8 = .{
-            .url = "https://github.com/lightpanda-io/zig-v8-fork/archive/refs/tags/v0.3.4.tar.gz",
-            .hash = "v8-0.0.0-xddH6_F3BAAiFvKY6R1H-gkuQlk19BkDQ0--uZuTrSup",
+            .url = "https://github.com/lightpanda-io/zig-v8-fork/archive/910b5f52d3968873580a850bd5c5f3705fbc8eed.tar.gz",
+            .hash = "v8-0.0.0-xddH63R8BAC8DIpYQEw97NJ2u9VbGGJT7X-OlrDpycwx",
         },
         // .v8 = .{ .path = "../zig-v8-fork" },
         .brotli = .{