fix(extensions): MaskExtension compatilble with TerrainExtension

[felixpalmer]

Background

Currently if the MaskExtension is used with TerrainExtension no draped layer is drawn. This PR fixes that:

@Pessimistress a change here might want to consider across the board is moving dummyTexture creation. I've tested this pattern this for other effects/extensions and it works - but will leave it for a follow-up PR if you're happy with the approach here

Change List

• Do not hardcode effects: [] in TerrainPass to allow MaskEffect configuration through
• Prevent TerrainEffect from including itself after effects: [] removal
• Move dummy texture creation outside of TerrainEffect instead reference global instance

[coveralls]

coverage: 81.443% (+0.008%) from 81.435% — felix/mask-with-terrain into master

[Pessimistress]

I would execute extreme caution when using any singleton involving GPU resources. There could be multiple Deck instances on the same page, each using their own device.