Improve/Fix CDP navigation event order

These changes all better align with chrome's event ordering/timing.

There are two big changes. The first is that our internal page_navigated event,
which is kind of our heavy hitter, is sent once the header is received as
opposed to (much later) on document load. The main goal of this internal event
is to trigger the "Page.frameNavigated" CDP event which is meant to happen
once the URL is committed, which _is_ on header response.

To accommodate this earlier trigger, new explicit events for DOMContentLoaded
and load have be added.

This drastically changes the flow of events as things go from:
Start Page Navigation
Response Received
  Start Frame Navigation
  Response Received
  End Frame Navigation
End Page Navigation
context clear + reset
DOMContentLoaded
Loaded

TO:
Start Page Navigation
Response Received
End Page Navigation
context clear + reset
Start Frame Navigation
Response Received
End Frame Navigation
DOMContentLoaded
Loaded

So not only does it remove the nesting, but it ensures that the context are
cleared and reset once the main page's navigation is locked in, and before any
frame is created.

src/cdp/CDP.zig

@@ -432,6 +432,8 @@ pub fn BrowserContext(comptime CDP_T: type) type {
             try notification.register(.page_navigate, self, onPageNavigate);
             try notification.register(.page_navigated, self, onPageNavigated);
             try notification.register(.page_frame_created, self, onPageFrameCreated);
+            try notification.register(.page_dom_content_loaded, self, onPageDOMContentLoaded);
+            try notification.register(.page_loaded, self, onPageLoaded);
         }
 
         pub fn deinit(self: *Self) void {
@@ -607,6 +609,16 @@ pub fn BrowserContext(comptime CDP_T: type) type {
             return @import("domains/page.zig").pageFrameCreated(self, msg);
         }
 
+        pub fn onPageDOMContentLoaded(ctx: *anyopaque, msg: *const Notification.PageDOMContentLoaded) !void {
+            const self: *Self = @ptrCast(@alignCast(ctx));
+            return @import("domains/page.zig").pageDOMContentLoaded(self, msg);
+        }
+
+        pub fn onPageLoaded(ctx: *anyopaque, msg: *const Notification.PageLoaded) !void {
+            const self: *Self = @ptrCast(@alignCast(ctx));
+            return @import("domains/page.zig").pageLoaded(self, msg);
+        }
+
         pub fn onPageNetworkIdle(ctx: *anyopaque, msg: *const Notification.PageNetworkIdle) !void {
             const self: *Self = @ptrCast(@alignCast(ctx));
             return @import("domains/page.zig").pageNetworkIdle(self, msg);