Improve VAO extension test

This commit makes the following improvements to the VAO extension test:
-Adds testing switching between VAOs that have different number of arrays
enabled.
-Uses a color attribute instead of using a texture coordinate attribute
which is meaningless since a texture is not used.
-Refactors testing pixels to remove unnecessary indirection.
-Fixes typos and makes the test output more descriptive.
Is this increase to the tolerance from 2 to 5 strictly necessary?