Use spawn not exec to run commands (#88)

* minor: use spawn to stream larger output rather than exec which buffers it

* test: verify distinct error code is returned from large output test

* test: breakout additional integration tests to run in parallel

* test: dont pass/fail PRs for coverage yet

sample.env

@@ -1,7 +1,11 @@
+# these are the bare minimum envvars required
 INPUT_TIMEOUT_MINUTES=1
 INPUT_MAX_ATTEMPTS=3
 INPUT_COMMAND="node -e 'process.exit(99)'"
-INPUT_RETRY_WAIT_SECONDS=10
-SHELL=pwsh
-INPUT_POLLING_INTERVAL_SECONDS=1
-INPUT_RETRY_ON=any
+INPUT_CONTINUE_ON_ERROR=false
+
+# these are optional
+#INPUT_RETRY_WAIT_SECONDS=10
+#SHELL=pwsh
+#INPUT_POLLING_INTERVAL_SECONDS=1
+#INPUT_RETRY_ON=any