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/cdp/domains/security.zig

@@ -44,7 +44,7 @@ fn setIgnoreCertificateErrors(cmd: anytype) !void {
 const testing = @import("../testing.zig");
 
 test "cdp.Security: setIgnoreCertificateErrors" {
-    var ctx = testing.context();
+    var ctx = try testing.context();
     defer ctx.deinit();
 
     _ = try ctx.loadBrowserContext(.{ .id = "BID-9" });