Plugins: Unsigned chromium file should not invalidate signature for Renderer plugin (#59104)

* Plugins: Unsigned chromium file should not invalidate signature for Renderer plugin

* fix test

* re-work solution

pkg/plugins/manager/testdata/renderer-added-file/plugin/MANIFEST.txt

@@ -0,0 +1,28 @@
+
+-----BEGIN PGP SIGNED MESSAGE-----
+Hash: SHA512
+
+{
+  "manifestVersion": "2.0.0",
+  "signatureType": "grafana",
+  "signedByOrg": "grafana",
+  "signedByOrgName": "Grafana Labs",
+  "plugin": "test-renderer",
+  "version": "1.0.0",
+  "time": 1669116992691,
+  "keyId": "7e4d0c6a708866e7",
+  "files": {
+    "plugin.json": "2f8fc554d0a080b9719ba43c0a8df366a88500eb129dfd4aedd9e3d147178273"
+  }
+}
+-----BEGIN PGP SIGNATURE-----
+Version: OpenPGP.js v4.10.10
+Comment: https://openpgpjs.org
+
+wrgEARMKAAYFAmN8tEAAIQkQfk0ManCIZucWIQTzOyW2kQdOhGNlcPN+TQxq
+cIhm576UAgiedgIhpOgTi/ypYgg8AtGQqKAwnDuDRDrYOc6LUDuskbSsR+J7
+f2QjcPGpPk3alaqiTYMxixkTgmD01hltaTJ0AwIJAS9XkKHKxC9/ZhSHYemw
+7wUeKs6AEvKR6amYZ+TF2pVyiJ9cEnl9J55MmDikqKFrIqC9J0V9r9wFkPAF
+kOKVOY+y
+=gqF+
+-----END PGP SIGNATURE-----

pkg/plugins/manager/testdata/renderer-added-file/plugin/chrome-win/debug.log

@@ -0,0 +1 @@
+TEST LOG LINE

pkg/plugins/manager/testdata/renderer-added-file/plugin/plugin.json

@@ -0,0 +1,11 @@
+{
+  "type": "renderer",
+  "name": "Test",
+  "id": "test-renderer",
+  "backend": true,
+  "executable": "test",
+  "info": {
+    "version": "1.0.0",
+    "description": "Test"
+  }
+}