Merge pull request from GHSA-7r3h-m5j6-3q42

* use uuid as our multiline env delimiter

* remove extra fn

* Fix version

* also throw error if delimiter is found in name or value

* move delimiter and uuid to global var in test

* upgrade uuid to newest version

* remove spy variable

* Update packages/core/src/core.ts

Co-authored-by: Thomas Boop <52323235+thboop@users.noreply.github.com>

* Update packages/core/src/core.ts

Co-authored-by: Thomas Boop <52323235+thboop@users.noreply.github.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@actions/core",
-  "version": "1.9.0",
+  "version": "1.9.1",
   "description": "Actions core lib",
   "keywords": [
     "github",
@@ -36,9 +36,11 @@
     "url": "https://github.com/actions/toolkit/issues"
   },
   "dependencies": {
-    "@actions/http-client": "^2.0.1"
+    "@actions/http-client": "^2.0.1",
+    "uuid": "^8.3.2"
   },
   "devDependencies": {
-    "@types/node": "^12.0.2"
+    "@types/node": "^12.0.2",
+    "@types/uuid": "^8.3.4"
   }
 }