Removes CDPT (generic CDP)

CDPT used to be a generic so that we could inject Browser, Session, Page and
Client. At some point, it [thankfully] became a generic only to inject Client.

This commit removes the generic and bakes the *Server.Client instance in CDP.
It uses a socketpair for testing.

BrowserContext is still generic, but that's generic for a very different reason
and, while I'd like to remove that generic too, it belongs in a different PR.

src/network/websocket.zig

@@ -324,7 +324,9 @@ pub const WsConnection = struct {
     pub fn init(socket: posix.socket_t, allocator: Allocator, json_version_response: []const u8, timeout_ms: u32) !WsConnection {
         const socket_flags = try posix.fcntl(socket, posix.F.GETFL, 0);
         const nonblocking = @as(u32, @bitCast(posix.O{ .NONBLOCK = true }));
-        assert(socket_flags & nonblocking == nonblocking, "WsConnection.init blocking", .{});
+        if (builtin.is_test == false) {
+            assert(socket_flags & nonblocking == nonblocking, "WsConnection.init blocking", .{});
+        }
 
         var reader = try Reader(true).init(allocator);
         errdefer reader.deinit();