resources: Add more details to .Err

This commit adds a .Data object (a map with `Body`, `StatusCode` etc.) to the .Err returned from `resources.GetRemote`, which means you can now do:

```
{{ with .Err }}
{{ range $k, $v := .Data }}
{{ end }}
{{ end }}
```

Fixes #9708

hugolib/page.go

@@ -133,7 +133,7 @@ func (p *pageState) reusePageOutputContent() bool {
 	return p.pageOutputTemplateVariationsState.Load() == 1
 }
 
-func (p *pageState) Err() error {
+func (p *pageState) Err() resource.ResourceError {
 	return nil
 }