Changes to support ARKit exposing the camera frames

[judax]

and rendering them in ARView.

Changes Proposed:

ARView now is able to determine if iOS is exposing the camera frames and render them similarly as how WebARonARCore does (but using the correct sampler and texture targets, not the external image OES extension)

Fixes:

Checklist:

• [X] Tested on WebARonARCore
• [X] Tested on WebARonARKit
• [X] I've read CONTRIBUTING.md and signed the CLA (required)
• [X] This PR does not contain built changes in dist/\* (required)
• [X] This PR only contains one commit (required)

[judax]

Pushed some changes to adapt to the WebARonARKit review.

[jsantell]

Nit: linting failure in ARView: 267:54 error Trailing spaces not allowed no-trailing-spaces

[judax]

Pushed a new revision addressing some of the concerns by @jsantell (that should be enjoying his PTO!!!)