Reland "Decouple gl_BaseVertex/gl_BaseInstance uniforms"

This reverts commit 10e5f34d14.

Reason for revert: exonerated from flaky crash suspect

Original change's description:
> Revert "Decouple gl_BaseVertex/gl_BaseInstance uniforms"
>
> This reverts commit 36bf1ebe5e.
>
> Reason for revert: suspect causing flaky crashes
>
> Bug: angleproject:6763
>
> Original change's description:
> > Decouple gl_BaseVertex/gl_BaseInstance uniforms
> >
> > These are builtin uniforms removed in
> > https://github.com/KhronosGroup/WebGL/pull/3278
> >
> > Decouple them from the original ANGLE_base_vertex_base_instance
> > extension.
> >
> > Make a new ANGLE_base_vertex_base_instance_shader_builtin
> > extension for these builtin uniforms.
> >
> > Bug: angleproject:3402
> > Change-Id: I77b93917976ce435db9c578c0ade37bff18a42b0
> > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3290304
> > Commit-Queue: Shrek Shao <shrekshao@google.com>
> > Reviewed-by: Geoff Lang <geofflang@chromium.org>
> > Reviewed-by: Kenneth Russell <kbr@chromium.org>
>
> Bug: angleproject:3402
> Change-Id: I75830baa14cf4e7c53750fd14ff76501145b4823
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3315610
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
> Reviewed-by: Kenneth Russell <kbr@chromium.org>
> Commit-Queue: Shrek Shao <shrekshao@google.com>

Bug: angleproject:6763
Bug: angleproject:3402
Change-Id: Ie436dc5d55364e464897d407a53b793941cd5d0b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3321703
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>

scripts/extension_data/intel_630_linux.json

@@ -5,6 +5,7 @@
     "ShaderLanguageVersion": "OpenGL ES GLSL ES 3.20 (ANGLE 2.1.16847 git hash: a097ee2ea7a9)",
     "Extensions": [
         "GL_ANGLE_base_vertex_base_instance",
+        "GL_ANGLE_base_vertex_base_instance_shader_builtin",
         "GL_ANGLE_client_arrays",
         "GL_ANGLE_compressed_texture_etc",
         "GL_ANGLE_copy_texture_3d",

scripts/extension_data/intel_630_win10.json

@@ -5,6 +5,7 @@
     "ShaderLanguageVersion": "OpenGL ES GLSL ES 3.20 (ANGLE 2.1.16846 git hash: 22d8115a208b)",
     "Extensions": [
         "GL_ANGLE_base_vertex_base_instance",
+        "GL_ANGLE_base_vertex_base_instance_shader_builtin",
         "GL_ANGLE_client_arrays",
         "GL_ANGLE_compressed_texture_etc",
         "GL_ANGLE_copy_texture_3d",

scripts/extension_data/nvidia_p400_linux.json

@@ -5,6 +5,7 @@
     "ShaderLanguageVersion": "OpenGL ES GLSL ES 3.20 (ANGLE 2.1.16847 git hash: a097ee2ea7a9)",
     "Extensions": [
         "GL_ANGLE_base_vertex_base_instance",
+        "GL_ANGLE_base_vertex_base_instance_shader_builtin",
         "GL_ANGLE_client_arrays",
         "GL_ANGLE_copy_texture_3d",
         "GL_ANGLE_depth_texture",

scripts/extension_data/nvidia_p400_win10.json

@@ -5,6 +5,7 @@
     "ShaderLanguageVersion": "OpenGL ES GLSL ES 3.20 (ANGLE 2.1.16847 git hash: a097ee2ea7a9)",
     "Extensions": [
         "GL_ANGLE_base_vertex_base_instance",
+        "GL_ANGLE_base_vertex_base_instance_shader_builtin",
         "GL_ANGLE_client_arrays",
         "GL_ANGLE_copy_texture_3d",
         "GL_ANGLE_depth_texture",

scripts/extension_data/pixel_4_android_11.json

@@ -5,6 +5,7 @@
     "ShaderLanguageVersion": "OpenGL ES GLSL ES 3.20 (ANGLE 2.1.16847 git hash: a097ee2ea7a9)",
     "Extensions": [
         "GL_ANGLE_base_vertex_base_instance",
+        "GL_ANGLE_base_vertex_base_instance_shader_builtin",
         "GL_ANGLE_client_arrays",
         "GL_ANGLE_compressed_texture_etc",
         "GL_ANGLE_copy_texture_3d",

scripts/extension_data/swiftshader_win10.json

@@ -5,6 +5,7 @@
     "ShaderLanguageVersion": "OpenGL ES GLSL ES 3.10 (ANGLE 2.1.16782 git hash: 368c0ce94472)",
     "Extensions": [
         "GL_ANGLE_base_vertex_base_instance",
+        "GL_ANGLE_base_vertex_base_instance_shader_builtin",
         "GL_ANGLE_client_arrays",
         "GL_ANGLE_compressed_texture_etc",
         "GL_ANGLE_copy_texture_3d",

scripts/extension_data/swiftshader_win10_gles1.json

@@ -5,6 +5,7 @@
     "ShaderLanguageVersion": "OpenGL ES GLSL ES 1.00 (ANGLE 2.1.16782 git hash: 368c0ce94472)",
     "Extensions": [
         "GL_ANGLE_base_vertex_base_instance",
+        "GL_ANGLE_base_vertex_base_instance_shader_builtin",
         "GL_ANGLE_client_arrays",
         "GL_ANGLE_compressed_texture_etc",
         "GL_ANGLE_depth_texture",