Add NFR scale test to GitHub actions pipeline

Problem:
Scale test is not part of Github actions pipeline

Solution:
- Add NFR scale test to GitHub actions pipeline along other NFR tests.
- Increase the size of the cluster used for NFR tests, as the scale
  test requires bigger size.

Testing:
- Successfully run with NGINX -- #2002
- Successfully run with NGINX Plus -- #2017

Some scale test issues were discovered:
- #2023
- #2009

Closes #1927

Author: pleshakov

.github/workflows/nfr.yml

@@ -8,7 +8,7 @@ on:
         required: true
         default: all
         type: choice
-        options: [performance, upgrade, all]
+        options: [performance, upgrade, scale, all]
       version:
         description: Version of NGF under test
         required: true
@@ -129,6 +129,8 @@ jobs:
         echo "PLUS_ENABLED=${{ inputs.nginx_plus }}" >> vars.env
         echo "GINKGO_LABEL=" >> vars.env
         echo "NGF_VERSION=${{ inputs.version }}" >> vars.env
+        echo "GKE_NUM_NODES=12" >> vars.env
+        echo "GKE_MACHINE_TYPE=n2d-standard-16" >> vars.env
 
     - name: Create GKE cluster
       working-directory: ./tests