Split E2E into default and full

Following the pattern from other repos, split the E2E test job into a
default job that runs a single default-only test always on PRs and a
full job that runs the full matrix when the ready-to-test label is
added.

Signed-off-by: Daniel Farrell <dfarrell@redhat.com>

.github/workflows/e2e.yml

@@ -1,5 +1,5 @@
 ---
-name: End to End Tests
+name: End to End Default
 
 on:
   pull_request:
@@ -9,26 +9,12 @@ jobs:
     name: E2E
     timeout-minutes: 30
     runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        cable_driver: ['libreswan', 'wireguard', 'vxlan']
-        globalnet: ['', 'globalnet']
-        k8s_version: ['1.17']
-        lighthouse: ['', 'lighthouse']
-        include:
-          - k8s_version: '1.18'
-          - k8s_version: '1.19'
-          - k8s_version: '1.20'
     steps:
       - name: Check out the repository
         uses: actions/checkout@v2
 
       - name: Run E2E deployment and tests
         uses: submariner-io/shipyard/gh-actions/e2e@devel
-        with:
-          k8s_version: ${{ matrix.k8s_version }}
-          using: ${{ matrix.cable_driver }} ${{ matrix.globalnet }} ${{ matrix.lighthouse }}
 
       - name: Post mortem
         if: failure()