More clarity on layers versus styles

[qgib]

Author Name: Jonathan Moules (Jonathan Moules)
Original Redmine Issue: 21041
Affected QGIS version: 3.4.3
Redmine category:web_services_clients/wms

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This WMS:
http://ogc.geo-ide.developpement-durable.gouv.fr/wxs?map=%2Fopt%2Fdata%2Fcarto%2Fgeoide-catalogue%2F1.4%2Forg_38102%2F2f3f11f0-91c9-479a-b748-ed1098603e91.internet.map&version=1.3.0

If you go all the way down to opening ID 7/8, you see layers named/titled:
"default" and "inspire_common:dEFAULT" - but neither of these is layers, they're styles. But they're represented here as though they're layers.

Including styles in this fashion only confuses pontentially already very confusing layer lists.
(for example - try figuring out what's a layer and what's a style in this getcap:
http://ags-sdi-public.jrc.ec.europa.eu/arcgis/services/world-release4-ETRS89/MapServer/WMSServer?version=1.3.0 )