The parameters to glCopyImageSubData are flexible and
can take a TextureID or a RenderbufferID as a GLuint.

Our replay needs to remap those values, so we'll convert the GLuint
based on the target.  This leads to a change like the following.

Before:

  glCopyImageSubData(138, 0x0DE1, 0, 0, 0, 0,
                     642, 0x0DE1, 1, 0, 0, 0,
                     256, 256, 1);

After:

  glCopyImageSubData(gTextureMap[138], 0x0DE1, 0, 0, 0, 0,
                     gTextureMap[642], 0x0DE1, 1, 0, 0, 0,
                     256, 256, 1);

Test: PUBG Mobile MEC
Bug: angleproject:6087
Bug: angleproject:6104
Change-Id: I5cd422e41ffbb4f08c8909e520bdce63e3008c5a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2981464
Commit-Queue: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>