Remove defunct built-in Leaflet layers

[JeroenDeDauw]

Several built-in leaflet-providers layers point at tile services that have shut down, so they only clutter the layer selector with entries that fail to load. This removes them from $egMapsLeafletAvailableLayers and $egMapsLeafletAvailableOverlayLayers:

• Stamen (service shut down October 2023; gone from leaflet-providers)
• Hydda (discontinued 2020; gone from leaflet-providers)
• MapQuest Open (shut down 2016; gone from leaflet-providers)
• OpenMapSurfer (gone from leaflet-providers)
• HikeBike and OpenStreetMap.BlackAndWhite (hosted on the decommissioned tiles.wmflabs.org)
• GeoportailFrance (the wxs.ign.fr endpoint has been retired)
• Esri.DeLorme (base map retired by Esri)

The matching $egMapsLeafletLayersApiKeys and $egMapsLeafletLayerDependencies entries for MapQuest Open and GeoportailFrance are dropped too. No source or test code references any of these names.

Users who relied on any of these can define a replacement with the $egMapsLeafletLayerDefinitions setting added in 13.1.0.

Targeted at 13.2.0 in the release notes; adjust if you would rather ship it as a patch.

_{AI-authored — Claude Code, Opus 4.8 (max); one-line ask from @JeroenDeDauw, no revisions; diff not yet human-reviewed; defunct status verified by DNS resolution + tile-fetch tests and absence from the bundled leaflet-providers, php/PHPUnit unavailable locally so syntax and tests rely on CI.}