NME : Use flag IgnoreTexturesAtLoadTime in ReflectionTextureBaseBlock

[GMM-Monumento]

When creating ReflectionTextureBaseBlock from a JSON NME material, if the flag NodeMaterial.IgnoreTexturesAtLoadTime is activated, this pull request prevents texture loading.

This new behavior is similar to the ones already existing in TextureBlock, ImageSourceBlock or TriPlanarBlock.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

Snapshot stored with reference name:
refs/pull/13409/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13409/merge/index.html

To test a playground add it to the URL, for example:

https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13409/merge/index.html#WGZLGJ#4600

Links to test babylon tools with this snapshot:

https://playground.babylonjs.com/?snapshot=refs/pull/13409/merge
https://sandbox.babylonjs.com/?snapshot=refs/pull/13409/merge
https://gui.babylonjs.com/?snapshot=refs/pull/13409/merge
https://nme.babylonjs.com/?snapshot=refs/pull/13409/merge

To test the snapshot in the playground with a playground ID add it after the snapshot query string:

https://playground.babylonjs.com/?snapshot=refs/pull/13409/merge#BCU1XR#0