Update to latest test agent and use signed Docker image. (#10982)

Update to latest test agent and use signed Docker image.

Fixed review notes.

Co-authored-by: sarah.chen <sarah.chen@datadoghq.com>

Author: AlexeyKuznetsov-DD

.gitlab-ci.yml

@@ -647,7 +647,7 @@ muzzle-dep-report:
     CI_USE_TEST_AGENT: "true"
     CI_AGENT_HOST: local-agent
   services:
-    - name: ghcr.io/datadog/dd-apm-test-agent/ddapm-test-agent:v1.33.1
+    - name: registry.ddbuild.io/images/mirror/dd-apm-test-agent/ddapm-test-agent:v1.44.0
       alias: local-agent
       variables:
         LOG_LEVEL: "DEBUG"