[6.x] Multisite bulk localize entries

[jaygeorge]

Description of the Problem

On multisite entry listings, going through each entry to duplicate them for a new site is slow. There’s no bulk way to add a localization for a selected site across multiple entries.

As per statamic/ideas#613

What this PR Does

• Adds a bulk Localize action on entry listings when multisite is enabled and at least one selected entry is missing a localization:
• Shows a site select with only sites still missing for the selection
• Creates localizations via makeLocalization for entries that don’t already exist in that site
• Skips entries that already have the localization, and reports how many were created vs skipped
• Hides the action when the selection isn’t eligible (mixed collections, fully localized, single-site collections, etc.)
• Fixes Publish Field.vue so hide_display + required fields don’t show a stray asterisk (used by the site select in the modal)

How to Reproduce

• Enable multisite with a collection available in multiple sites (e.g. en, fr, de).
• Create several entries that exist only in one site.
• Open the collection entry index, select those entries, and choose Localize.
• Pick a missing site and confirm — localizations are created for entries that need them; existing ones are skipped.