[ci] Convert version presubmit check to LUCI (#4822)

Adds a LUCI version of the version presubmit check, using the new label passthrough functionality, and removes it from Cirrus. Since that was the last Cirrus task, this removes the entire Cirrus config, and the associated Dockerfile.

Part of https://github.com/flutter/flutter/issues/130076

.ci/Dockerfile

@@ -1,6 +0,0 @@
-# The Flutter version is not important here, since the CI scripts update Flutter
-# before running. What matters is that the base image is pinned to minimize
-# unintended changes when modifying this file.
-FROM cirrusci/flutter@sha256:d99b1ba2602240a74722970b5c0cd704bbe60a7eba7557157c784f2f693c393f
-
-RUN apt-get update -y

.ci/scripts/check_version.sh

@@ -4,14 +4,13 @@
 # found in the LICENSE file.
 set -e
 
-# For pre-submit, this is currently run in Cirrus; see TODO below.
+# For pre-submit, check for missing or breaking changes that don't have a
+# corresponding override label.
 # For post-submit, ignore platform interface breaking version changes and
 # missing version/CHANGELOG detection since PR-level overrides aren't available
 # in post-submit.
 if [[ $LUCI_PR == "" ]]; then
   ./script/tool_runner.sh version-check --ignore-platform-interface-breaks
 else
-  # TODO(stuartmorgan): Migrate this check from Cirrus. See
-  # https://github.com/flutter/flutter/issues/130076
-  :
+  ./script/tool_runner.sh version-check --check-for-missing-changes --pr-labels="$PR_OVERRIDE_LABELS"
 fi

.ci/targets/repo_checks.yaml

@@ -44,13 +44,14 @@ tasks:
     script: script/tool_runner.sh
     args: ["dependabot-check"]
     always: true
-  - name: publishability
-    script: script/tool_runner.sh
-    args: ["publish-check", "--allow-pre-release"]
-    always: true
   - name: CHANGELOG and version validation
     script: .ci/scripts/check_version.sh
     always: true
   - name: federated safety check
     script: .ci/scripts/check_federated_safety.sh
     always: true
+  # This is the slowest test, so prefer keeping it last.
+  - name: publishability
+    script: script/tool_runner.sh
+    args: ["publish-check", "--allow-pre-release"]
+    always: true

.cirrus.yml

@@ -1,34 +0,0 @@
-gcp_credentials: ENCRYPTED[!9409b709ab4de7293a70606cca13eaf42e9cbc704e8a6b4e3d2b09484cf997cbd2334e1eeafe23626ad07a726106df90!]
-
-# Run on PRs and main branch post submit only. Don't run tests when tagging.
-only_if: $CIRRUS_TAG == '' && ($CIRRUS_PR != '' || $CIRRUS_BRANCH == 'main')
-
-setup_template: &SETUP_TEMPLATE
-  upgrade_flutter_script:
-    - PINNED_VERSION=$(< .ci/flutter_master.version)
-    # Ensure that the repository has everything.
-    - cd $FLUTTER_HOME
-    - git config remote.origin.fetch "+refs/heads/*:refs/remotes/origin/*"
-    - git fetch origin
-    # Switch to the pinned master version.
-    - git checkout $TARGET_TREEISH
-    # Run doctor to allow auditing of what version of Flutter the run is using.
-    - flutter doctor -v
-  tool_setup_script:
-    - .ci/scripts/prepare_tool.sh
-
-task:
-  << : *SETUP_TEMPLATE
-  gke_container:
-    dockerfile: .ci/Dockerfile
-    builder_image_name: docker-builder-linux # gce vm image
-    builder_image_project: flutter-cirrus
-    cluster_name: test-cluster
-    zone: us-central1-a
-    namespace: default
-  matrix:
-    # TODO(stuartmorgan): Migrate this to LUCI; See check_version.sh.
-    - name: version_check
-      only_if: $CIRRUS_PR != ''
-      version_script:
-        - ./script/tool_runner.sh version-check --check-for-missing-changes --pr-labels="$CIRRUS_PR_LABELS"