Dependencies seem to be incorrectly tracked in some Intel OpenGL
drivers (on macOS specifically), causing crashes in glDeleteTextures
if a GL command buffer is being constructed where those textures are
destinations of CopyTexImage2D/CopyTexSubImage2D. Work around this bug
by flushing before texture deletion if CopyTex{Sub}Image have been
called recently. The tracking is only done on a per-context rather
than a per-device basis, but seems sufficient to work around the
problem as identified.

Tested both with new ANGLE test on affected hardware, and in WebKit's
ANGLE backend for WebGL. Works around the crash reported in
https://bugs.webkit.org/show_bug.cgi?id=205707 .

Bug: angleproject:4267
Change-Id: I2266a5590759f6a3f19080def08710ef4b66d463
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1987932
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>