Add fixed elevation range per dataset group mode for mesh layers (Request in QGIS)

[qgis-bot]

Request for documentation

From pull request qgis/QGIS#56977 Author: @nyalldawson QGIS version: 3.38

Add fixed elevation range per dataset group mode for mesh layers

PR Description:

This mimics the "fixed range per band" mode we have for raster layers, but allows a per-dataset group elevation range to be set for mesh layers

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