[vector layers][ui] Expose the features sorting order expression driving the features display ordering within the attribute table views and relation editor widgets (Request in QGIS)

[qgis-bot]

Request for documentation

From pull request qgis/QGIS#63916 Author: @nirvn QGIS version: 4.0

** [vector layers][ui] Expose the features sorting order expression driving the features display ordering within the attribute table views and relation editor widgets**

PR Description:

Description

This PR exposes the sorting order expression driving the features display ordering within the attribute table views and relation editor widgets into the vector layer properties dialog within its display panel. Here's how it looks:

This makes the setting for more discoverable and manageable. For the attribute table's dual view and relation editor widget, that setting is also closely tied with the display name used in the features list.

Note: the PR temporarily includes the improvements from https://github.com/qgis/QGIS/pull/63901 , I'll rebase once that is merged

Commits tagged with [need-docs] or [FEATURE]