Modify compute shader grid setup.

Modify compute shader grid setup.

Modify how the grid is set up for compute shader draw indirect test,
in order to avoid verfication failures due to difference in
floating-point computations on the CPU vs the GPU.

The existing code assumes infinite FP precision.

This change will guarantee the next value of pos(X) to be equal to
the first value of pos(X+1), avoiding gaps/discontinuities.

Affects:
dEQP-GLES31.functional.draw_indirect.compute_interop.large.drawarrays_combined_grid_1000x1000_drawcount_1
dEQP-GLES31.functional.draw_indirect.compute_interop.large.drawarrays_combined_grid_1000x1000_drawcount_5000
dEQP-GLES31.functional.draw_indirect.compute_interop.large.drawarrays_combined_grid_1000x1000_drawcount_8
dEQP-GLES31.functional.draw_indirect.compute_interop.large.drawarrays_separate_grid_1000x1000_drawcount_1
dEQP-GLES31.functional.draw_indirect.compute_interop.large.drawarrays_separate_grid_1000x1000_drawcount_5000
dEQP-GLES31.functional.draw_indirect.compute_interop.large.drawarrays_separate_grid_1000x1000_drawcount_8

Bug: 71515808
Change-Id: I21fe8ec9ea48b15f6171265df802bc47be775f56