Revert "Use a single FBO for EXT_multisampled_render_to_texture targets"

This reverts commit 949dfb5ffd953a5302099af0a839737e59519fb8.

Reason for revert: Reverting to revert parent CL.

Original change's description:
> Use a single FBO for EXT_multisampled_render_to_texture targets
>
> Uses a single FBO and changes the attachments based on whether we need
> multisample or not. This is an effort to work around presumed driver
> bugs from having the same texture bound to different FBOs with different
> sample counts.
>
> Bug: chromium:1222095
> Change-Id: I1347a149524be95181a4d3fb0a0da7bfe92a2ec9
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/442737
> Commit-Queue: Jim Van Verth <jvanverth@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

Bug: chromium:1222095
Change-Id: I1647c21d04348daae1636d7e637faf6fa604b0df
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/450196
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
2 files changed