Resolution and tileSize

**maptalks's version and what browser you use?**
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v0.47.0

**Issue description**
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In openlayers and mapbox, when tileSize is changed(e.g. from 256 to 512), resolution will be also adjusted to ensure the extent of a tile is the same.

This is different from maptalks's implementation.

Need to dig in.

**Please provide a reproduction URL (on any jsfiddle like site)**
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