Use GL_ANGLE_base_vertex_base_instance

Adds the ANGLE extension to our list of options for
glDraw*BaseInstance.

Removes glDrawElementsInstancedBaseInstance since this method is not
supported by the ANGLE extension.

Change-Id: Ifd25324feeaad55a4d141b5064bcd8e059948ef7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/280388
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
7 files changed