HackStudio/LanguageServers: Move some components out of Cpp

This makes them available for use by other language servers.
Also as a bonus, update the Shell language server to discover some
symbols and add go-to-definition functionality :^)

Userland/DevTools/HackStudio/LanguageServers/Shell/main.cpp

@@ -55,9 +55,5 @@ int main(int, char**)
         perror("unveil");
         return 1;
     }
-    if (unveil(nullptr, nullptr) < 0) {
-        perror("unveil");
-        return 1;
-    }
     return event_loop.exec();
 }