Update workflow to verify fmt

To support this, I refactored the actions to use a composite action so
that all checks could run with the same setup.

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

.github/actions/prepare/action.yml

@@ -0,0 +1,26 @@
+name: 'Prepare Warewulf'
+description: 'Prepare environment and Warewulf source code for testing and building'
+inputs:
+  go-version:
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Install gpgme (dependency)
+      run: sudo apt-get install libgpgme-dev
+      shell: bash
+
+    - name: Setup go ${{ inputs.go-version }}
+      uses: actions/setup-go@v3
+      with:
+        go-version: ${{ inputs.go-version }}
+        cache: true
+
+    - name: Configure Warewulf
+      run: make config
+      shell: bash
+
+    - name: Prepare vendor directory
+      run: make vendor
+      shell: bash