docs: list the remaining type renames in the v8 upgrade guide

[imkath]

Closes #2550.

The v8 section covers the *Layer and *SourceRaw renames but misses a few more, so code that compiled on 7.x breaks with no hint in the guide.

I diffed the type exports of 7.1.9 against 8.1.3 (/mapbox, /mapbox-legacy and /maplibre) and checked every old and new name with tsc:

• added AnyLayer, AnySource, RasterSource, RasterDemSource and MapboxStyle to the existing table (RasterDEMSourceSpecification is spelled differently in mapbox-legacy)
• a second table for the Mapbox-only names; /maplibre still exports the MapLayer*Event types
• a note that the source classes are no longer re-exported
• a note on LayerProps: the field wasn't removed, the type now includes CustomLayerInterface, so reading metadata needs a type !== 'custom' check

[greptile-apps]

Confidence Score: 5/5

[Low impact] This documentation-only change appears safe to merge.

Summary

Expands the v8 upgrade guide with the remaining type renames.

• The v8 guide lists more renamed style and source types.
• The v8 guide lists renamed types for Mapbox imports.
• The v8 guide points source-class imports to the base map packages.
• The v8 guide shows how to check a layer before reading its metadata.

No actionable issues found.

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