This cl enables the sampleRateShading feature.

New test failures caused by enabling sampleRateShading:
Tests: dEQP-VK.glsl.builtin_var.fragdepth.*

List of affected tests now passing:
Tests: dEQP-VK.glsl.builtin_var.fragcoord_msaa.*
Tests: dEQP-VK.pipeline.multisample.min_sample_shading.*.samples_4.*
Tests: dEQP-VK.pipeline.multisample.mixed_count.*
Tests: dEQP-VK.pipeline.multisample.variable_rate.*
Tests: dEQP-VK.pipeline.multisample_interpolation.*.samples_4
Tests: dEQP-VK.pipeline.multisample_interpolation.sample_interpolate_at_single_sample.*.samples_1
Tests: dEQP-VK.pipeline.multisample_shader_builtin.*.samples_4
Tests: dEQP-VK.pipeline.multisample_shader_builtin.write_sample_mask.*
Tests: dEQP-VK.renderpass.suballocation.sampleread.numsamples_4.*
Tests: dEQP-VK.renderpass2.suballocation.sampleread.numsamples_4.*

Bug: b/171415086
Change-Id: I1aa50cff9e2fada482ceef594c59641c7243b563
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/51469
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Commit-Queue: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>