Implement support for Nested Forms entry meta

[rafaehlers]

I thought we had proper support for their entry, but apparently not.

Let's add support for these three so when creating a View for a "child" form, these can be easily added to the View:

We need to support these as fields/columns and within the Merge Tag picker:

and

When trying to filter entries by that entry meta via the [gravityview search_field="parent_entry_id" search_value] shortcode and the View field of GravityView, it doesn't work either:

Related:

• https://community.gravityforms.com/t/created-view-to-search-child-form-entries-but-need-to-show-parent-entry-id/15797/3
• https://gravitywiz.com/documentation/gravity-forms-nested-forms/#the-parent-merge-tag

[rafaehlers]

Also related: https://github.com/GravityKit/GravityView/issues/1136

[floatytheastronaut]

FreeScout #77545.
https://support.gravitykit.com/conversation/77545?folder_id=4

[rafaehlers]

Released in 2.23 https://github.com/GravityKit/GravityView/releases/tag/v2.23 and customer notified ✅