Fetches WMTS GetCapabilities asynchronously, then applies the basemap.
Uses _styleGeneration as a stale-switch guard (if the user switches away
before resolution, the result is discarded).
Any previous in-flight request is aborted before starting a new one.
Fetches WMTS GetCapabilities asynchronously, then applies the basemap. Uses
_styleGenerationas a stale-switch guard (if the user switches away before resolution, the result is discarded). Any previous in-flight request is aborted before starting a new one.