Add .clang-format files and format more files

The .clang-format files tell clang-format to ignore certain directories
(replacing code in lint_clang_format.sh which will be removed).

$ git ls-tree -r master --name-only | grep '\.\(c\|h\|cpp\|gn\|gni\|mm\|m\|py\)$' | xargs ./append-space-to-files
$ git checkout -- generator/templates third_party/khronos/{KHR,vulkan}
$ git cl format --full --python

Followed by manual reformatting of a few things in Python for
readability.

Bug: none
Change-Id: I4c9e472cc9a5cd80c07286e808f4e597cfef5428
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/24785
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>

third_party/.clang-format

@@ -0,0 +1,2 @@
+DisableFormat: true
+SortIncludes: false

third_party/khronos/BUILD.gn

@@ -41,9 +41,7 @@ config("khronos_headers_public") {
 }
 
 source_set("khronos_platform") {
-  sources = [
-    "KHR/khrplatform.h",
-  ]
+  sources = [ "KHR/khrplatform.h" ]
 
   public_configs = [ ":khronos_headers_public" ]
 }