As these are touched by pixel shaders, this is extraordinarily hot code, and the cost of ref-counting by shared_ptr can really impact performance.

As the const cache is updated at well known sync points, the queryConstCache method is safe to return a raw pointer to the routine.

Bug: b/137524292
Bug: b/137649247
Change-Id: I2ae1f159467eb27b918344714cef1963f3b24a45
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/34453
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Ben Clayton <bclayton@google.com>