Implement Bentley glTF vendor extensions

[pmconne]

For our hackathon I'm trying to implement the encoding and decoding of the remaining glTF extensions we need to support iModels in glTF.

• EXT_textureInfo_constant_lod
• BENTLEY_material_line_style
  • For lines
  • For edges
  • Pending completion of Implementation for BENTLEY_materials_line_style #8856, I am temporarily only supporting patterns included in LinePixels enum.
• BENTLEY_material_point_style
• Prerequisite: support encoding and decoding points

Most of the changes are in the encoding, implemented in a separate TilesetPublisher PR.

[pmconne]

Lines with pattern and width.

[pmconne]

Wide edges and points with diameter of 2 pixels.

[pmconne]

This was used during the hackathon to test the encoding changes. It is redundant with #8856.