Revert "Use ManagedBackendTexture in place of TestUtils backend texture helpers."

This reverts commit 5ee0556048a10d3bea818042094d92356d256b53.

Reason for revert: breaking bots

Original change's description:
> Use ManagedBackendTexture in place of TestUtils backend texture helpers.
>
> Unify on a single family of helpers for making backend textures.
>
> Stresses callback systems in more tests by avoiding artificial
> flush/submit/syncs.
>
> some misc test cleanup along the way.
>
> Change-Id: Ia692e8927ba97b391ee77ea06ebf437a555617b2
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/324710
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,bsalomon@google.com

Change-Id: I7d4fc9412c870ae13f7498671379b871dbf5a6c4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/325619
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
24 files changed