When draw buffers set to GL_NONE, instead of remove the attachment from
renderpass which breaks renderpass, we force vulkan's per buffer color
mask to false while keep the disabled draw buffer attached. This CL also
always create FrameBuffer with all color attachments regardless it is
enabled or not.

Bug: b/167301719
Change-Id: Ice9fca9aacf774a47d13b749f822b222cc050174
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2389007Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Charlie Lao <cclao@google.com>