To avoid creating aliasing views for sRGB textures, the ImageCopy
texture will do/undo sRGB transformation such that the final result is
as-if both source and destination views were linear.

Possible future optimizations:

- If either of source or destination has already been created with the
  MUTABLE flag, i.e. has a linear view already available, that can be
  used.
- If destination is sRGB but not renderable while its corresponding
  linear format is, and if the image is already created with the MUTABLE
  flag, using the linear view would allow the copy to go through the GPU
  instead of the CPU.

Bug: b/157934810
Bug: angleproject:4092
Change-Id: I43aaf882c90e1c60d0d9eb04636c203fc04090a4
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2241622Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>