ci: Update CI to stash changes before checkout (#12210)

.circleci/config.yml

@@ -690,10 +690,15 @@ jobs:
               git config --local user.email "github-team-consul-core@hashicorp.com"
               git config --local user.name "hc-github-team-consul-core"
               
+              # stash newly built bindata_assetfs.go
+              git stash push
+              
               # checkout the CI branch and merge latest from main
               git checkout ci/main-assetfs-build
               git merge --no-edit main
             
+              git stash pop
+            
               short_sha=$(git rev-parse --short HEAD)
               git add agent/uiserver/bindata_assetfs.go
               git commit -m "auto-updated agent/uiserver/bindata_assetfs.go from commit ${short_sha}"