Previously we were checking whether all attachments have a format which
requires clamping. We now support the independentBlend feature, and
independent clamping, so we can optimize the blend state more granularly
and not miss opportunities.

Bug: b/140193782
Change-Id: I7e663fd8ebc6a7a6e35133c0c4c5cad84278eeb3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/47828
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>