This reverts commit a61e273a.

Reason for revert: Causes rendering artifacts in "Aztec Ruins".

Bug: angleproject:4444

Original change's description:
> Vulkan: Fix store ops with linear command recording.
> 
> DiscardFramebuffer was being ignored in the new linear path. Fix this
> by using the correct APIs. Also cleans up some of the access to the
> "RenderPassCommandBuffer" struct in ContextVk. Add a new accessor that
> returns the RenderPass without a flush that ensures it is only called
> when a RenderPass is already started.
> 
> Bug: angleproject:4029
> Change-Id: Ibd199f3a371c0f91b448a0b34c8752dc8b76c284
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2057329
> Reviewed-by: Charlie Lao <cclao@google.com>
> Commit-Queue: Jamie Madill <jmadill@chromium.org>

TBR=tobine@google.com,jmadill@chromium.org,cclao@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: angleproject:4029
Change-Id: I7d925b88c438a20ebe4a48634568addda7a64d60
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2093157Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>
Reviewed-by: Charlie Lao <cclao@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>