Clang-format codebase (#1684)

This applies clang-format to the whole codebase.

I noticed we have .clang-format in wabt but the codebase is not very
well formatted. This kind of mass-formatting PR has fans and skeptics
because it can mess with `git blame`, but we did a similar thing in
Binaryen a few years ago (WebAssembly/binaryen#2048, which was merged in
WebAssembly/binaryen#2059) and it was not very confusing after all.
If we are ever going to format the codebase, I think it is easier to do
it in a single big PR than dozens of smaller PRs.

This is using the existing .clang-format file in this repo, which
follows the style of Chromium. If we think this does not suit the
current formatting style, we can potentially tweak .clang-format too.
For example, I noticed the current codebase puts many `case` statements
within a single line when they are short, but the current .clang-format
does not allow that.

This does not include files in src/prebuilt, because they are generated.

This also manually fixes some comment lines, because mechanically
applying clang-format to long inline comments can look weird.

I also added a clang-format check hook in the Github CI in #1683, which
I think can be less controversial, given that it only checks the diff.

---

After discussions, we ended up reverting many changes, especially
one-liner functions and switch-cases, which are too many to wrap in
`// clang-format off` and `// clang-format on`. I also considered fixing
`.clang-format` to allow those one-liners but it caused a larger churn
in other parts. So currently the codebase does not conform to
`.clang-format` 100%, but we decided it's fine.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/type.h b/src/type.h
index 64c71c7e..d9b662aa 100644
--- a/src/type.h
+++ b/src/type.h
@@ -120,7 +120,7 @@ class Type {
   //   (type $T (func (result i32 i64)))
   //   ...
   //   (block (type $T) ...)
-  // 
+  //
   bool IsIndex() const { return static_cast<int32_t>(enum_) >= 0; }
 
   Index GetIndex() const {