Add new draw elements base vertex tests

Add new draw elements base vertex tests

New tests for EXT_draw_elements_base_vertex extension
exercising the following draw calls

- DrawElementsBaseVertex()
- DrawRangeElementsBaseVertex()
- DrawElementsInstancedBaserVertex()

New test groups:
- dEQP-GLES31.functional.draw_elements_base_vertex.*

New tests:
- indices.*
- base_vertex.*
- builtin_variable.*
- points.*
- triangles.*
- triangle_fan.*
- triangle_strip.*
- lines.*
- line_strip.*
- line_loop.*

Extend dEQP-GLES31.functional.debug.negative_coverage.callbacks.vertex_array.*
tests to include additional mapping and mismatched primitive mode
errors for base vertex draw calls.

New tests:
- *.primitive_mode_mismatch
- *.invalid_map

Change-Id: Iefc9bcddd3fe8831d2bb20f2e46d06f92daa6d6b