[Extensions] Add GetInstalledExtension() method to ExtensionRegistry

This CL adds GetInstalledExtension() method to ExtensionRegistry and
uses it instead of deprecated ExtensionService::GetInstalledExtension()
in chrome/browser/ui/app_list/.

Part of removing the deprecated GetInstalledExtension() call
from the ExtensionService.

BUG=489687

Review URL: https://codereview.chromium.org/1130353010

Cr-Commit-Position: refs/heads/master@{#333036}
void AppListControllerDelegate::GetApps(Profile* profile,
                                        extensions::ExtensionSet* out_apps) {
  ExtensionRegistry* registry = ExtensionRegistry::Get(profile);
  DCHECK(registry);
  out_apps->InsertAll(registry->enabled_extensions());
  out_apps->InsertAll(registry->disabled_extensions());
  out_apps->InsertAll(registry->terminated_extensions());
}

void AppListControllerDelegate::GetApps(Profile* profile,
                                        extensions::ExtensionSet* out_apps) {
  ExtensionRegistry* registry = ExtensionRegistry::Get(profile);
  DCHECK(registry);
  out_apps->InsertAll(registry->enabled_extensions());
  out_apps->InsertAll(registry->disabled_extensions());
  out_apps->InsertAll(registry->terminated_extensions());
}
