The depthClamp feature allows users to force the depth to fit between
two values. Enabling depth clamping disables primitive depth clipping
unless a user explicitly enables both.

Bug: b/181655689
Tests: dEQP-VK.glsl.builtin_var.fragdepth.*
Tests: dEQP-VK.clipping.clip_volume.depth_clamp.*
Tests: dEQP-VK.draw.inverted_depth_ranges.*
Tests: dEQP-VK.draw.depth_clamp.*
Change-Id: Ib184b1972a11db2a806b7985754075fff55b4461
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/53929Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Sean Risser <srisser@google.com>
Commit-Queue: Sean Risser <srisser@google.com>