.github: Replace PR workflows with stubs that call reusables

The PR workflows now are just stubs that call reusable
workflows located in the asterisk-ci-actions repo.

(cherry picked from commit b133383389)

.github/workflows/OnPRStateChanged.yml

@@ -0,0 +1,59 @@
+#
+# Workflows, like this one, that are triggered by PRs submitted
+# from forked repositories are severly limited in what they can do
+# for security reasons. For instance, they can't add or remove
+# labels or comments even on the PR that triggered them.  Since
+# we need to both of those things, GitHub recommends creating a
+# separate workflow that does those tasks that's triggered when
+# this PR workflow starts or finishes. Since that workflow isn't
+# being run in the context of a forked repo, it has all the
+# privileges needed to add and remove labels and comments.  The
+# accompanying OnPRStateChangedPriv workflow does just that.
+
+name: PRStateChanged
+run-name: "PR ${{github.event.number}} ${{github.event.action}} by ${{ github.actor }}"
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+concurrency:
+  group: ${{github.workflow}}-${{github.event.number}}
+  cancel-in-progress: true
+
+jobs:
+#
+# Pull requests created from forked respositories don't have access
+# to the "Action Variables" ('vars' context) so we need to retrieve
+# control data from an action that's located in asterisk-ci-actions.
+#
+  Setup:
+    runs-on: ubuntu-latest
+    outputs:
+      vars:  ${{ steps.setvars.outputs.control_data }}
+    steps:
+      - id: setvars
+        uses: asterisk/asterisk-ci-actions/GetRepoControlData@main
+        with:
+          repo: ${{ github.event.repository.name}}
+      - name: DumpEnvironment
+        uses: asterisk/asterisk-ci-actions/DumpEnvironmentAction@main
+        with:
+          action-vars: ${{ toJSON(steps.setvars.outputs) }}
+
+  PRCheck:
+    name: PRCheck
+    needs: Setup
+    uses: asterisk/asterisk-ci-actions/.github/workflows/AsteriskUnitGateTest.yml@main
+    with:
+      test_type:         prstatechange
+      asterisk_repo:     ${{github.repository}}
+      pr_number:         ${{github.event.number}}
+      base_branch:       ${{github.event.pull_request.base.ref}}
+      build_options:     ${{ fromJSON(needs.Setup.outputs.vars).BUILD_OPTIONS }}
+      unittest_command:  ${{ fromJSON(needs.Setup.outputs.vars).UNITTEST_COMMAND }}
+      testsuite_repo:    ${{ fromJSON(needs.Setup.outputs.vars).TESTSUITE_REPO }}
+      gatetest_list:     ${{ fromJSON(needs.Setup.outputs.vars).GATETEST_LIST }}
+      gatetest_commands: ${{ fromJSON(needs.Setup.outputs.vars).GATETEST_COMMANDS }}
+    secrets:
+      TOKEN: ${{ secrets.GITHUB_TOKEN }}
+