Update images, fix extrapath (#723)

* fix: typo

* fix: remove debug for git references

it generates a massive amount of logs

* feat: read values from env

allows to test act on GHA when it's not a main repo

* fix: merge extrapath with PATH

* fix(tests): add additional shells for testing

* fix(image): update images

pin node to major version only, current node version: 12.22.1
replace most images with `node:12-buster-slim` to prevent
errors on macOS runner due to DockerHub pull limit
replace ocaml image

Co-authored-by: Casey Lee <cplee@nektos.com>

pkg/runner/testdata/uses-docker-url/push.yml

@@ -5,7 +5,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - uses: docker://alpine:3.13
-      with:
-        somekey: somevalue
-        args: echo ${INPUT_SOMEKEY} | grep somevalue
+      - uses: docker://node:12-buster-slim
+        with:
+          somekey: somevalue
+          args: echo ${INPUT_SOMEKEY} | grep somevalue