Use agent test tool snapshot Docker image instead of building in CI (#133)

diff --git a/tests/plugin/docker/Dockerfile.tool b/tests/plugin/docker/Dockerfile.tool
deleted file mode 100644
index e88d0ca..0000000
--- a/tests/plugin/docker/Dockerfile.tool
+++ /dev/null
@@ -1,44 +0,0 @@
-#
-# Licensed to the Apache Software Foundation (ASF) under one or more
-# contributor license agreements.  See the NOTICE file distributed with
-# this work for additional information regarding copyright ownership.
-# The ASF licenses this file to You under the Apache License, Version 2.0
-# (the "License"); you may not use this file except in compliance with
-# the License.  You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-
-FROM openjdk:8
-
-WORKDIR /tests
-
-ARG COMMIT_HASH=8a48c49b4420df5c9576d2aea178b2ebcb7ecd09
-
-ADD https://github.com/apache/skywalking-agent-test-tool/archive/${COMMIT_HASH}.tar.gz .
-
-RUN tar -xf ${COMMIT_HASH}.tar.gz --strip 1
-
-RUN rm ${COMMIT_HASH}.tar.gz
-
-RUN ./mvnw -B -DskipTests package
-
-FROM openjdk:8
-
-EXPOSE 19876 12800
-
-WORKDIR /tests
-
-COPY --from=0 /tests/dist/skywalking-mock-collector.tar.gz /tests
-
-RUN tar -xf skywalking-mock-collector.tar.gz --strip 1
-
-RUN chmod +x bin/collector-startup.sh
-
-ENTRYPOINT bin/collector-startup.sh
diff --git a/tests/plugin/docker/docker-compose.base.yml b/tests/plugin/docker/docker-compose.base.yml
index 7a2a09f..ce44b0b 100644
--- a/tests/plugin/docker/docker-compose.base.yml
+++ b/tests/plugin/docker/docker-compose.base.yml
@@ -19,10 +19,7 @@
 
 services:
   collector:
-    build:
-      context: .
-      dockerfile: Dockerfile.tool
-    image: skywalking-collector:ci
+    image: ghcr.io/apache/skywalking-agent-test-tool/mock-collector:2ed17bb73eb993cc7d4effa7a5a36dd91a9ec8cd
     ports:
       - 19876:19876
       - 12800:12800