New GHA e2e test functionality

.github/workflows/test-runner-gha-job.yaml

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+name: Test Runner
+
+on:
+  workflow_dispatch:
+
+env:
+  TAG: "latest"
+
+jobs:
+  test:
+    runs-on: ["self-hosted", "Linux", "x64", "e2e-gha-tester"]
+
+    steps:
+      - name: echoer
+        run: |
+          echo I am a thing
+          echo I have finished being a thing

e2e/integrations/github/readme-gha.MD

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+# How to implement GitHub e2e GHA Tests for KEDA
+
+Assumes you have already completed readme.MD
+
+## Actions workflows:
+
+You will need to modify the .env file to include the following variables:
+
+.env file is located in the kedacore/tests directory.
+
+- `GH_GHA_WORKFLOW_ID=` This is the workflow id of the workflow to run for scaled gha jobs. (test-runner-gha-job.yaml)
+- `GH_APP_ID=` This is the app id of the github app that is used to create the runners.
+- `GH_INST_ID=` This is the installation id of the github app that is used to create the runners.
+- `GH_APP_KEY=` This is the private key of the github app that is used to create the runners.
+
+### Run this after the test-tools PR is merged to main to get the workflow id for the workflow to run for scaled gha job.
+1. `curl https://api.github.com/repos/kedacore/test-tools/actions/workflows`
+
+2. Create a new github app for this repo. You need the app id when you have created it; turn off webhooks when you set it up.
+3. Create a private key for the app and save it to a file. You need the private key when you have created it, base64 it and add it to the above env variable
+4. Install the app on the repo. You need the installation id when you have installed it (Its in the URL at the top)
+5. Permissions - Actions Read Only, Admin Read & Write, Metadata Read Only (in repositories)