Move ast_type.cc to type.cc.

This file is already in the ast/ folder, and has been marked as a TODO
to move for a while. Actually move.

Change-Id: I697ff903fc9906921e2768243bdfba581cf18d4e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/117589
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/tint/BUILD.gn

@@ -547,7 +547,6 @@ libtint_source_set("libtint_ast_src") {
     "ast/array.h",
     "ast/assignment_statement.cc",
     "ast/assignment_statement.h",
-    "ast/ast_type.cc",  # TODO(bclayton) - rename to type.cc
     "ast/atomic.cc",
     "ast/atomic.h",
     "ast/attribute.cc",
@@ -698,6 +697,7 @@ libtint_source_set("libtint_ast_src") {
     "ast/texture.cc",
     "ast/texture.h",
     "ast/traverse_expressions.h",
+    "ast/type.cc",
     "ast/type.h",
     "ast/type_decl.cc",
     "ast/type_decl.h",

src/tint/CMakeLists.txt

@@ -84,7 +84,6 @@ list(APPEND TINT_LIB_SRCS
   ast/array.h
   ast/assignment_statement.cc
   ast/assignment_statement.h
-  ast/ast_type.cc  # TODO(bclayton) - rename to type.cc
   ast/atomic.cc
   ast/atomic.h
   ast/attribute.cc
@@ -233,6 +232,7 @@ list(APPEND TINT_LIB_SRCS
   ast/type_decl.h
   ast/type_name.cc
   ast/type_name.h
+  ast/type.cc
   ast/type.h
   ast/u32.cc
   ast/u32.h