Issue #3589219: Migrate leftover store_in_public_file_directory on data_export subclass displays

Summary

Adds a follow-up post-update views_data_export_post_update_remap_subclass_display_filesystem that catches store_in_public_file_directory keys left behind on data_export subclass displays (e.g. data_export_excel from views_data_export_excel) by the original views_data_export_post_update_remap_display_filesystem, which filtered on the exact plugin id data_export.

The new function matches on the presence of the legacy key rather than the plugin id, so it covers any current or future subclass without hardcoding sister-module ids.

Risk

Idempotent: skips displays without store_in_public_file_directory. Same migration logic as the original post-update (NULL or truthy -> public, anything else -> private).

Test plan

• Pipeline passes.
• On a site with leftover legacy keys on data_export_excel displays, after drush updb the keys are gone and Configuration Inspector returns no errors for those views.