fix: ensure all post steps are executed (#1286)

This fixes an issue in the chain of post steps introduced
while updating the step-logger for composite actions.

It includes a test case so we make sure this does not happen
again.

pkg/runner/testdata/ensure-post-steps/action-post/action.yml

@@ -0,0 +1,11 @@
+name: "action post"
+description: "action post"
+inputs:
+  fail:
+    description: "true if this should fail"
+    required: false
+    default: "false"
+runs:
+  using: node16
+  main: "./main.js"
+  post: "./post.js"

pkg/runner/testdata/ensure-post-steps/action-post/post.js

@@ -0,0 +1,3 @@
+if (process.env["INPUT_FAIL"] === "true") {
+  process.exit(1);
+}