Revert prefix name and add ci- prefix

Author: sarahchen6

.gitlab-ci.yml

@@ -30,7 +30,7 @@ variables:
   MAVEN_REPOSITORY_PROXY: "https://depot-read-api-java.us1.ddbuild.io/magicmirror/magicmirror/@current/"
   GRADLE_PLUGIN_PROXY: "https://depot-read-api-java.us1.ddbuild.io/magicmirror/magicmirror/@current/"
   BUILDER_IMAGE_REPO: "registry.ddbuild.io/images/mirror/dd-trace-java-docker-build" # images are pinned in images/mirror.lock.yaml in the DataDog/images repo
-  TESTER_IMAGE_VERSION_PREFIX: "" # set only when testing a new build from the dd-trace-java-docker-build repo (e.g. "138_merge-" corresponds to PR #138)
+  BUILDER_IMAGE_VERSION_PREFIX: "ci-" # use either an empty string (e.g. "") for latest images or a version followed by a hyphen (e.g. "ci-" or "123_merge-")
   REPO_NOTIFICATION_CHANNEL: "#apm-java-escalations"
   DEFAULT_TEST_JVMS: /^(8|11|17|21|25|tip)$/ # the latest "tip" version is 26
   PROFILE_TESTS:
@@ -143,7 +143,7 @@ default:
     fi
 
 .gradle_build: &gradle_build
-  image: ${BUILDER_IMAGE_REPO}:${TESTER_IMAGE_VERSION_PREFIX}base
+  image: ${BUILDER_IMAGE_REPO}:${BUILDER_IMAGE_VERSION_PREFIX}base
   stage: build
   variables:
     MAVEN_OPTS: "-Xms256M -Xmx1024M"
@@ -219,7 +219,7 @@ default:
 # on the central publisher portal, it invalidates the old one. This check prevents going further.
 # See https://datadoghq.atlassian.net/wiki/x/Oog5OgE
 maven-central-pre-release-check:
-  image: ${BUILDER_IMAGE_REPO}:${TESTER_IMAGE_VERSION_PREFIX}base
+  image: ${BUILDER_IMAGE_REPO}:${BUILDER_IMAGE_VERSION_PREFIX}base
   stage: .pre
   rules:
     - if: '$CI_COMMIT_TAG =~ /^v[0-9]+\.[0-9]+\.[0-9]+$/'
@@ -400,7 +400,7 @@ config-inversion-linter:
 
 test_published_artifacts:
   extends: .gradle_build
-  image: ${BUILDER_IMAGE_REPO}:${TESTER_IMAGE_VERSION_PREFIX}7 # Needs Java7 for some tests
+  image: ${BUILDER_IMAGE_REPO}:${BUILDER_IMAGE_VERSION_PREFIX}7 # Needs Java7 for some tests
   stage: tests
   needs: [ build ]
   variables:
@@ -567,7 +567,7 @@ muzzle-dep-report:
 
 .test_job:
   extends: .gradle_build
-  image: ${BUILDER_IMAGE_REPO}:${TESTER_IMAGE_VERSION_PREFIX}$testJvm
+  image: ${BUILDER_IMAGE_REPO}:${BUILDER_IMAGE_VERSION_PREFIX}$testJvm
   tags: [ "docker-in-docker:amd64" ] # use docker-in-docker runner for testcontainers
   needs: [ build_tests ]
   stage: tests
@@ -795,7 +795,7 @@ test_smoke_semeru8_debugger:
     testJvm: "semeru8"
 
 aggregate_test_counts:
-  image: ${BUILDER_IMAGE_REPO}:${TESTER_IMAGE_VERSION_PREFIX}base
+  image: ${BUILDER_IMAGE_REPO}:${BUILDER_IMAGE_VERSION_PREFIX}base
   stage: test-summary
   # Note: No explicit 'needs' or 'dependencies' required
   # By default, GitLab CI automatically downloads artifacts from ALL jobs in previous stages