Revert "Mark wrapped textures imported into SkImages as "read only"."

This reverts commit 796693af3cda0e24a76a89a092ed8de0e46ccb18.

Reason for revert: texture flags assertion in DDL config

Original change's description:
> Mark wrapped textures imported into SkImages as "read only".
> 
> Read only textures and proxies fail writePixels, as copy dsts, and mip
> regeneration.
> 
> Bug: skia:8509
> 
> Change-Id: Iaa0b473cc9a9930fde3ef0e91373d5040650de35
> Reviewed-on: https://skia-review.googlesource.com/c/174316
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>

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

Change-Id: If5cb36e83795656185ff8d26e4ef2c52a2695a09
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:8509
Reviewed-on: https://skia-review.googlesource.com/c/174846
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
53 files changed