chore(ci): Install Go/goimports as codegen dependencies (#1713)

Author: robin-aws

.github/actions/install_smithy_dafny_codegen_dependencies/action.yml

@@ -30,6 +30,16 @@ runs:
         python -m pip install --upgrade black
         python -m pip install --upgrade docformatter
 
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: "1.23"
+
+    - name: Install Go imports
+      shell: bash
+      run: |
+        go install golang.org/x/tools/cmd/goimports@latest
+
     # Without this the if-dafny-at-least command includes "Downloading ..." output
     - name: Arbitrary makefile target to force downloading Gradle
       shell: bash