refactor: GITHUB_ENV command / remove env.PATH (#1503)

* fix: GITHUB_ENV / PATH handling

* apply workaround

* add ctx to ApplyExtraPath

* fix: Do not leak step env in composite

See https://github.com/nektos/act/pull/1585 for a test

* add more tests

---------

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

pkg/runner/testdata/docker-action-custom-path/push.yml

@@ -0,0 +1,12 @@
+on: push
+jobs:
+  _:
+    runs-on: ubuntu-latest
+    steps:
+    - run: |
+        FROM ubuntu:latest
+        ENV PATH="/opt/texlive/texdir/bin/x86_64-linuxmusl:${PATH}"
+        ENV ORG_PATH="${PATH}"
+        ENTRYPOINT [ "bash", "-c", "echo \"PATH=$PATH\" && echo \"ORG_PATH=$ORG_PATH\" && [[ \"$PATH\" = \"$ORG_PATH\" ]]" ]
+      shell: mv {0} Dockerfile
+    - uses: ./