Fix closure compiler warnings with -sFULL_ES3 (#26893)

Without this we see
```
building:ERROR: /tmp/emscripten_temp/hello_world.js:14723:8: WARNING - [JSC_UNREACHABLE_CODE] unreachable code
  14723|         GLctx.bufferSubData(target, mapping.offset, HEAPU8.subarray(mapping.mem, mapping.mem+mapping.length));
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```

The `if/else` stuff around `GLctx.bufferSubData` is pretty nasty so I
have a followup to tidy it up.

Also, include more of webgl in test_codesize_hello_dylink_all. It
obviously gets much bigger but its also means that we can use this to
observe codesize changes in more library code.

Author: sbc100

embuilder.py

@@ -81,6 +81,7 @@
     'libGL-emu-getprocaddr',
     'libGL-emu-webgl2-ofb-getprocaddr',
     'libGL-webgl2-ofb-getprocaddr',
+    'libGL-webgl2-ofb-full_es3-getprocaddr',
     'libGL-ww-getprocaddr',
     'libhtml5',
     'libsockets',

src/lib/libwebgl.js

@@ -3825,7 +3825,7 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
       cb.stride = stride;
       cb.ptr = ptr;
       cb.clientside = true;
-      cb.vertexAttribPointerAdaptor = function(index, size, type, normalized, stride, ptr) {
+      cb.vertexAttribPointerAdaptor = /** @this {WebGLRenderingContext} */ function(index, size, type, normalized, stride, ptr) {
         this.vertexAttribPointer(index, size, type, normalized, stride, ptr);
       };
       return;
@@ -4262,9 +4262,14 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if WEBGL_USE_GARBAGE_FREE_APIS
       if ({{{ isCurrentContextWebGL2() }}}) {
         GLctx.bufferSubData(target, mapping.offset, HEAPU8, mapping.mem, mapping.length);
-      } else
+      }
+#if INCLUDE_WEBGL1_FALLBACK
+      else
 #endif
+#endif
+#if INCLUDE_WEBGL1_FALLBACK
       GLctx.bufferSubData(target, mapping.offset, HEAPU8.subarray(mapping.mem, mapping.mem+mapping.length));
+#endif
     }
     _free(mapping.mem);
     mapping.mem = 0;

src/lib/libwebgl2.js

@@ -930,7 +930,7 @@ var LibraryWebGL2 = {
       cb.stride = stride;
       cb.ptr = ptr;
       cb.clientside = true;
-      cb.vertexAttribPointerAdaptor = function(index, size, type, normalized, stride, ptr) {
+      cb.vertexAttribPointerAdaptor = /** @this {WebGLRenderingContext} */ function(index, size, type, normalized, stride, ptr) {
         this.vertexAttribIPointer(index, size, type, stride, ptr);
       };
       return;