fix: Support TileLayer refinement strategies

[kylebarron]

Change list

• Define TileMetadata type in raster-tileset-2d for object returned by Tileset.getTileMetadata
• Return bbox object from getTileMetadata, which is the WGS84 bounding box (edge densified) of the current tile.
• Fix decimation calculation to consider both image size and cell size. For example, sentinel 2 has a different image size for its overviews (512x512) as for the full-resolution data (1024x1024). We need to handle this offset correctly.
• Add tests

Screen.Recording.2026-03-18.at.7.31.21.PM.mov

Closes #190, closes #192

[edeetee]

Thank you legend!