Use less nesting in many arrays of arrays tests.

Use less nesting in many arrays of arrays tests.

Testing 8 levels of array-of-array nesting is very thorough, but a bit
overkill.  It creates a huge amount of register pressure which tends to
slow down compilers, causing the test to take an unreasonable amount of
time to run.  This patch reduces it to 4 levels in many subtests, which
should still be a reasonable amount of testing while running in much
less time.

This cuts the runtime of KHR-GL46.arrays_of_arrays_gl.* by 33 minutes
(43 -> 10) on my laptop's discrete GPU.  With the Intel Mesa driver,
it cuts it by 17 minutes (23 -> 6).

Some tests still exercise 8 levels of nesting, so there's still some
coverage of that scenario.

Components: OpenGL
VK-GL-CTS issue: 878

Affects:
- KHR-GL4*.arrays_of_arrays_gl.InteractionFunctionCalls1
- KHR-GL4*.arrays_of_arrays_gl.InteractionFunctionCalls2
- KHR-GL4*.arrays_of_arrays_gl.InteractionArgumentAliasing1
- KHR-GL4*.arrays_of_arrays_gl.InteractionArgumentAliasing2
- KHR-GL4*.arrays_of_arrays_gl.InteractionArgumentAliasing3
- KHR-GL4*.arrays_of_arrays_gl.InteractionArgumentAliasing4
- KHR-GL4*.arrays_of_arrays_gl.InteractionArgumentAliasing5
- KHR-GL4*.arrays_of_arrays_gl.InteractionArgumentAliasing6
- KHR-GL4*.arrays_of_arrays_gl.SubroutineFunctionCalls1
- KHR-GL4*.arrays_of_arrays_gl.SubroutineFunctionCalls2
- KHR-GL4*.arrays_of_arrays_gl.SubroutineArgumentAliasing1
- KHR-GL4*.arrays_of_arrays_gl.SubroutineArgumentAliasing2
- KHR-GL4*.arrays_of_arrays_gl.SubroutineArgumentAliasing3
- KHR-GL4*.arrays_of_arrays_gl.SubroutineArgumentAliasing4
- KHR-GLES31.core.arrays_of_arrays.InteractionFunctionCalls1
- KHR-GLES31.core.arrays_of_arrays.InteractionFunctionCalls2
- KHR-GLES31.core.arrays_of_arrays.InteractionArgumentAliasing1
- KHR-GLES31.core.arrays_of_arrays.InteractionArgumentAliasing2
- KHR-GLES31.core.arrays_of_arrays.InteractionArgumentAliasing3
- KHR-GLES31.core.arrays_of_arrays.InteractionArgumentAliasing4
- KHR-GLES31.core.arrays_of_arrays.InteractionArgumentAliasing5
- KHR-GLES31.core.arrays_of_arrays.InteractionArgumentAliasing6

Change-Id: Ia26ac5fb94799a2f80c9e2e9553c066d9c13c59b