[transform] Move the transform folder

This CL moves the transform folder from src/ast to src/. The transforms
operate on the AST, but they aren't part of the AST so I think the top
level folder makes more sense.

This will possibly cause issues when rolling if the transform is being
used.

Change-Id: Ibd7c94474168a7a4bdf38321f4e12ad111c80323
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/28941
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 1110d6c..a1ed133 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -315,8 +315,6 @@
     "src/ast/struct_member_offset_decoration.h",
     "src/ast/switch_statement.cc",
     "src/ast/switch_statement.h",
-    "src/ast/transform/vertex_pulling_transform.cc",
-    "src/ast/transform/vertex_pulling_transform.h",
     "src/ast/type/alias_type.cc",
     "src/ast/type/alias_type.h",
     "src/ast/type/array_type.cc",
@@ -375,6 +373,8 @@
     "src/reader/reader.h",
     "src/scope_stack.h",
     "src/source.h",
+    "src/transform/vertex_pulling_transform.cc",
+    "src/transform/vertex_pulling_transform.h",
     "src/type_determiner.cc",
     "src/type_determiner.h",
     "src/type_manager.cc",
@@ -723,7 +723,6 @@
     "src/ast/struct_member_test.cc",
     "src/ast/struct_test.cc",
     "src/ast/switch_statement_test.cc",
-    "src/ast/transform/vertex_pulling_transform_test.cc",
     "src/ast/type/alias_type_test.cc",
     "src/ast/type/array_type_test.cc",
     "src/ast/type/bool_type_test.cc",
@@ -746,6 +745,7 @@
     "src/ast/variable_test.cc",
     "src/ast/workgroup_decoration_test.cc",
     "src/scope_stack_test.cc",
+    "src/transform/vertex_pulling_transform_test.cc",
     "src/type_determiner_test.cc",
     "src/type_manager_test.cc",
     "src/validator_control_block_test.cc",