feat: high level annotation api

[josxha]

• [x] remove web-only Marker
• [x] Marker text
• [x] Marker icon
• [x] Circle
• [x] Polyline
• [x] Polygon
• [x] Update example app

Some more cross references:

• https://github.com/maplibre/flutter-maplibre-gl/issues/436
• https://github.com/maplibre/flutter-maplibre-gl/discussions/292
• https://www.bam.tech/article/build-a-declarative-map-widget-above-the-mapbox-flutter-package-mapbox-maps-flutter

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