Water material: Fix support for mesh instances

[Popov72]

See https://forum.babylonjs.com/t/water-material-fix/41609/5

It also fixes use of bumpSuperimpose, fresnelSeparate and bumpAffectsReflection, which were not reset when switching their state from true to false.

[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]

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[sebavan]

woooah :-)