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/set-env-new-env-file-per-step/push.yml

@@ -0,0 +1,15 @@
+on: push
+jobs:
+  _:
+    runs-on: ubuntu-latest
+    env:
+      MY_ENV: test
+    steps:
+    - run: exit 1
+      if: env.MY_ENV != 'test'
+    - run: echo "MY_ENV=test2" > $GITHUB_ENV
+    - run: exit 1
+      if: env.MY_ENV != 'test2'
+    - run: echo "MY_ENV=returnedenv" > $GITHUB_ENV
+    - run: exit 1
+      if: env.MY_ENV != 'returnedenv'