Remove the generic nature of Env and most of the JS classes

Back in the zig-js-runtime days, globals were used for the state and webapi
declarations. This caused problems largely because it was done across
compilation units (using @import("root")...).

The generic Env(S, WebApi) was used to solve these problems, while still making
it work for different States and WebApis.

This change removes the generics and hard-codes the *Page as the state and
only supports our WebApis for the class declarations.

To accommodate this change, the runtime/*tests* have been removed. I don't
consider this a huge loss - whatever behavior these were testing, already
exists in the browser/**/*.zig web api.

As we write more complex/complete WebApis, we're seeing more and more cases
that need to rely on js objects directly (JsObject, Function, Promises, etc...).
The goal is to make these easier to use. Rather than using Env.JsObject, you
now import "js.zig" and use js.JsObject (TODO: rename JsObject to Object).
Everything is just a plain Zig struct, rather than being nested in a generic.

After this change, I plan on:

1 - Renaming the js objects, JsObject -> Object. These should be referenced in
    the webapi as js.Object, js.This, ...

2 - Splitting the code across multiple files (Env.zig, Context.zig,
    Caller.zig, ...)

src/cdp/cdp.zig

@@ -21,18 +21,17 @@ const Allocator = std.mem.Allocator;
 const json = std.json;
 
 const log = @import("../log.zig");
+const js = @import("../browser/js/js.zig");
+const polyfill = @import("../browser/polyfill/polyfill.zig");
+
 const App = @import("../app.zig").App;
-const Env = @import("../browser/env.zig").Env;
 const Browser = @import("../browser/browser.zig").Browser;
 const Session = @import("../browser/session.zig").Session;
 const Page = @import("../browser/page.zig").Page;
-const Inspector = @import("../browser/env.zig").Env.Inspector;
 const Incrementing = @import("../id.zig").Incrementing;
 const Notification = @import("../notification.zig").Notification;
 const InterceptState = @import("domains/fetch.zig").InterceptState;
 
-const polyfill = @import("../browser/polyfill/polyfill.zig");
-
 pub const URL_BASE = "chrome://newtab/";
 pub const LOADER_ID = "LOADERID24DD2FD56CF1EF33C965C79C";
 
@@ -329,7 +328,7 @@ pub fn BrowserContext(comptime CDP_T: type) type {
         node_registry: Node.Registry,
         node_search_list: Node.Search.List,
 
-        inspector: Inspector,
+        inspector: js.Inspector,
         isolated_worlds: std.ArrayListUnmanaged(IsolatedWorld),
 
         http_proxy_changed: bool = false,
@@ -661,7 +660,7 @@ pub fn BrowserContext(comptime CDP_T: type) type {
 /// An object id is unique across all contexts, different object ids can refer to the same Node in different contexts.
 const IsolatedWorld = struct {
     name: []const u8,
-    executor: Env.ExecutionWorld,
+    executor: js.ExecutionWorld,
     grant_universal_access: bool,
 
     // Polyfill loader for the isolated world.
@@ -695,7 +694,7 @@ const IsolatedWorld = struct {
             page,
             null,
             false,
-            Env.GlobalMissingCallback.init(&self.polyfill_loader),
+            js.GlobalMissingCallback.init(&self.polyfill_loader),
         );
     }