[gl] Rename interstage variables in the backend

This will slightly simplify the process of moving symbol renaming
completely into the backend, as Dawn will no longer have to pass in a
map of requested renames. These symbols are not visible from the API
side, so there is no reason to have Dawn set the names.

Bug: 380043958
Change-Id: Icb3484fc463e90272ce1abbf110c410bc69f2682
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/218618
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: James Price <jrprice@google.com>
diff --git a/test/tint/builtins/gen/var/textureLoad/49f76f.wgsl.expected.glsl b/test/tint/builtins/gen/var/textureLoad/49f76f.wgsl.expected.glsl
index 965bf96..3daec83 100644
--- a/test/tint/builtins/gen/var/textureLoad/49f76f.wgsl.expected.glsl
+++ b/test/tint/builtins/gen/var/textureLoad/49f76f.wgsl.expected.glsl
@@ -57,7 +57,7 @@
 };
 
 uniform highp usampler2DMS arg_0;
-layout(location = 0) flat out uvec4 vertex_main_loc0_Output;
+layout(location = 0) flat out uvec4 tint_interstage_location0;
 uvec4 textureLoad_49f76f() {
   uvec2 arg_1 = uvec2(1u);
   uint arg_2 = 1u;
@@ -78,6 +78,6 @@
   gl_Position = v_3.pos;
   gl_Position.y = -(gl_Position.y);
   gl_Position.z = ((2.0f * gl_Position.z) - gl_Position.w);
-  vertex_main_loc0_Output = v_3.prevent_dce;
+  tint_interstage_location0 = v_3.prevent_dce;
   gl_PointSize = 1.0f;
 }