Refactor cronjob controller to reduce duplication

Author: Mrtenz

packages/examples/packages/cronjobs/snap.manifest.json

@@ -7,7 +7,7 @@
     "url": "https://github.com/MetaMask/snaps.git"
   },
   "source": {
-    "shasum": "sw0ZFHz/Q1AJWcpz3yidRs1kcCLZloDZUfqWnjROaTU=",
+    "shasum": "0TR0Utkwc9o/2TKALOlQbjGVoJkrrXO1nP8l0gXDU88=",
     "location": {
       "npm": {
         "filePath": "dist/bundle.js",
@@ -20,7 +20,7 @@
     "endowment:cronjob": {
       "jobs": [
         {
-          "expression": "*/10 * * * * *",
+          "expression": "PT10S",
           "request": {
             "method": "execute"
           }

packages/snaps-controllers/package.json

@@ -99,6 +99,7 @@
     "async-mutex": "^0.5.0",
     "browserify-zlib": "^0.2.0",
     "concat-stream": "^2.0.0",
+    "cron-parser": "^4.5.0",
     "fast-deep-equal": "^3.1.3",
     "get-npm-tarball-url": "^2.0.3",
     "immer": "^9.0.6",