SF: Add workaround to release screenshot buffer

Works around driver behavior to force the [E]GL driver to fully release
the screenshot buffer immediately after the screenshot is complete
rather than deferring until the next instance of client composition.

Bug: b/77935566
Test: Manual, inspect 'dumpsys SurfaceFlinger' after launching an app
      and then returning home (which causes a screenshot for overview)

Change-Id: I4f33d89f3ff3020707a9f556a1fcfe34bc9b7adb