Move the `.clang-format` rule up one level from `./src` to `.`.
Add a `.clang-format` file to `./third_party` that disables formatting.
Update `./src/clang-format-all.sh` to include `./tests`.
Format all source files in `./tests`.

Bug: b/144825072
Change-Id: I01c7ae37a7b1fe8d63ee143107da8acefba20e76
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39873
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Tested-by: Ben Clayton <bclayton@google.com>