tint->dawn: Shuffle source tree in preperation of merging repos

docs/    -> docs/tint/
fuzzers/ -> src/tint/fuzzers/
samples/ -> src/tint/cmd/
src/     -> src/tint/
test/    -> test/tint/

BUG=tint:1418,tint:1433

Change-Id: Id2aa79f989aef3245b80ef4aa37a27ff16cd700b
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/80482
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>

test/tint/samples/function.wgsl

@@ -0,0 +1,21 @@
+// Copyright 2020 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+fn main() -> f32 {
+    return ((2. * 3.) - 4.) / 5.;
+}
+
+@stage(compute) @workgroup_size(2)
+fn ep() {
+}