Geometry shader inputs have an extra array dimension, which can be
unsized as it can be derived from the primitive type.  This change fixes
the grammar to support such arrays.

Additionally, it enables EXT_shader_io_blocks automatically with
EXT_geometry_shader and EXT_tessellation_shader per spec.

Bug: angleproject:3580
Change-Id: Ia7eb3e8be28c2eef2072dbe2a546fa34973104ab
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2568242Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>