Report stagingDir_is_custom to apply_staging_dir

[robin-ynput]

Changelog Description

Following #1069 and testing ynput/ayon-nuke#52, I realized apply_staging_dir was missing stagingDir_is_custom.

Testing notes:

The following ensure Nuke product can be published with custom staging directories.

1. Enable custom staging directory with some profiles ayon+settings://core/tools/publish/custom_staging_dir_profiles (make it persistent so you can troubleshoot)
2. Create a template matching the staging directory under ayon+anatomy://Dummy/templates/staging
   e.g. {root[work]}/{project[name]}/{hierarchy}/{folder[name]}/temp_render_only/{product[type]}/{product[name]}
3. Open Nuke and create+publish some products
4. Ensure that the staging directory is working is properly redirected to the relevant template for the associated products/task