Improve precision handling in texture.explicit_lod

Improve precision handling in texture.explicit_lod

This change improves precision requirement handling in
dEQP-VK.texture.explicit_lod test group by adding separate controls for
format conversion and filtering math.

Changed tests:
dEQP-VK.texture.explicit_lod.*

Components: Vulkan

Change-Id: Id64da1d63d87d02c73c757a3f2d5d50f2fbc19c0
(cherry picked from commit 4269dc0c1e513c550d3d45c16f2760450dfcef5c)