LibWeb+LibWebView+WebContent: Add an Inspector IPC to execute JavaScript

The Inspector will have an <input> element to execute user-provided JS.
This adds an IDL method and IPC to forward that JS from the Inspector
WebView to the Inspector client.

Userland/Services/WebContent/WebContentClient.ipc

@@ -72,5 +72,6 @@ endpoint WebContentClient
 
     inspector_did_load() =|
     inspector_did_select_dom_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement> pseudo_element) =|
+    inspector_did_execute_console_script(String script) =|
 
 }