fix: remote docker actions new action cache and dry run mode (#2513)

* fixes

* Add TestDockerCopyTarStreamDryRun

* increase coverage a bit

* fixup

* fixup

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

pkg/runner/testdata/remote-action-docker-new-cache/config/config.yml

@@ -0,0 +1 @@
+local-repositories: {}

pkg/runner/testdata/remote-action-docker-new-cache/push.yml

@@ -0,0 +1,10 @@
+name: remote-action-docker
+on: push
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/hello-world-docker-action@v1
+      with:
+        who-to-greet: 'Mona the Octocat'