Cherry-pick: Ensure edited scripts provided from the client with newl…

…ine switches and no other changes get converted to "\n" (#22196) (#22202)

Merged to `main` in #22199.

```
git checkout minor-fleet-v4.57.0
git checkout -b 22196-cherry-pick
git cherry-pick ea2a978
git push -u origin 22196-cherry-pick
```

ee/server/service/software_installers.go

@@ -241,16 +241,16 @@ func (svc *Service) UpdateSoftwareInstaller(ctx context.Context, payload *fleet.
 
  if installScript != existingInstaller.InstallScript {
  dirty["InstallScript"] = true
- payload.InstallScript = &installScript
  }
+ payload.InstallScript = &installScript
  }
 
  if payload.PostInstallScript != nil {
  postInstallScript := file.Dos2UnixNewlines(*payload.PostInstallScript)
  if postInstallScript != existingInstaller.PostInstallScript {
  dirty["PostInstallScript"] = true
- payload.PostInstallScript = &postInstallScript
  }
+ payload.PostInstallScript = &postInstallScript
  }
 
  if payload.UninstallScript != nil {
@@ -270,10 +270,10 @@ func (svc *Service) UpdateSoftwareInstaller(ctx context.Context, payload *fleet.
 
  preProcessUninstallScript(payloadForUninstallScript)
  if payloadForUninstallScript.UninstallScript != existingInstaller.UninstallScript {
- uninstallScript = payloadForUninstallScript.UninstallScript
  dirty["UninstallScript"] = true
- payload.UninstallScript = &uninstallScript
  }
+ uninstallScript = payloadForUninstallScript.UninstallScript
+ payload.UninstallScript = &uninstallScript
  }
 
  // persist changes starting here, now that we've done all the validation/diffing we can