1) Added new Multisampled Image Index. For the upcoming
multisampled array case, we cannot automatically create the same
MS image index during resolve. So the correct MS image index is created and
saved during the initial creation of the MS Texture. It seems to be more
streamlined as well, only creating the MS image index once, and not using
hardcoded values to get the subresourceIndex.
2) reordering resolveTextureHelper to remove duplicated code.

Bug: angleproject:3107
Change-Id: Ifd91136a64efb5e7bd296e09cd876a6e6eb8e77e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1919555
Commit-Queue: Rafael Cintron <rafael.cintron@microsoft.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>