Combine CRD install verification into 1 job, and update k8s versions (#3448)

* Validate CRDs against latest Kubernetes versions

Add Kubernetes v1.19 and v1.20 series images, and consolidate the job
into a single file to reduce repetition.

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Ignore job if the changes are only site/design

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Fix codespell error

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Cache Velero binary for reuse on workers

This will cache the Velero binary based on the PR number and a SHA256 of
the generated binary.

This way, the runners testing each version of Kubernetes do not need to
build it independently.

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Fix GitHub event access

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Wrap output path in quotes

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Move code checkout to build step

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Also cache go modules

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Fix syntax issues

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Download cached binary on each node

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Use cached go modules on main CI

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

.github/workflows/pr-ci-check.yml

@@ -1,14 +1,20 @@
 name: Pull Request CI Check
 on: [pull_request]
 jobs:
-
   build:
     name: Run CI
     runs-on: ubuntu-latest
     steps:
+      - name: Check out the code
+        uses: actions/checkout@v2
 
-    - name: Check out the code
-      uses: actions/checkout@v2
+      - name: Fetch cached go modules
+        uses: actions/cache@v2
+        with:
+          path: ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
 
-    - name: Make ci
-      run: make ci
+      - name: Make ci
+        run: make ci