Always regenerate go.work file (#20842)

We flip the default mode to always regenerate the file,
and expose an option to ignore if it exists.

```release-note
NONE
```

scripts/setup_go_work.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-if [[ ! -f "go.work" ]] ;
+if [[ $1 != "true" ]] ;
 then
     echo "Creating a go.work file"