Map component exhausts GL contexts

[hkfb]

The Map component is not able to share GL contexts with other components.

Should expose the GL context used and be able to share it with other components.

Cf. https://deck.gl/docs/api-reference/core/deck#gl

@t0oF @t0oF-azpn @vardit123y

[hkfb]

Deck.gl discussion: https://github.com/visgl/deck.gl/discussions/7557

[hkfb]

Some more ideas:

• Recycling the 3D canvas when the mouse cursor leaves it and replacing it with a snapshot
• Using scissor test for each viewport and overlaying the canvas fixed on top of the document. I believe this is an example: https://threejs.org/examples/webgl_multiple_elements.html