This entry point is specifically for retrieving very large timestamp
values from EXT_disjoint_time_query. In GLES 2.0 contexts with the
Vulkan back-end we were getting some astronomical values that couldn't
be cast to 32-bit ints.

Also fix missing dependencies in generate_loader.py.

Bug: angleproject:4433
Change-Id: I59146dcc1a163a24ac2d7c37546f4551a7a8890a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2080595
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>