Fix Icon Materials that Don't Respect Depth

[Cameron-Micka]

Overview

A handful of materials are using the GUI/Text Shader which does not respect the depth buffer. This results in icons drawing though other objects. This icons should use the MRTK/Standard shader and be marked as TransparentCutout or Transparent.

Changes

• Fixes: Some Icon Materials Don't Respect Depth #5521

Verification

1. Open the HandInteractionExamples scene.
2. Look at the ToggleFeaturesPanel from the backside.

As a reviewer, it is possible to check out this change locally by using the following
commands (substituting {PR_ID} with the ID of this pull request):

git fetch origin pull/{PR_ID}/head:name_of_local_branch

git checkout name_of_local_branch

[wiwei]

/azp run

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