Instead of updating images every time we write to them,
this cl adds a dirtiness mechanism, which will mark an
Image object as dirty for specific unique subresource
regions and then only actually perform the required
task (cube border update, decompression, ...) once the
image memory is accessed for reading.

Bug: b/159045555
Change-Id: I791a69529e4c2e78aa6562251020aa0bf978bd01
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/45188
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>