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/vk-gl-cts/graphicsfuzz/switch-with-empty-if-false/0.spvasm

@@ -0,0 +1,37 @@
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Fragment %main "main" %_GLF_color
+               OpExecutionMode %main OriginUpperLeft
+               OpSource ESSL 310
+               OpName %main "main"
+               OpName %_GLF_color "_GLF_color"
+               OpDecorate %_GLF_color Location 0
+       %void = OpTypeVoid
+          %5 = OpTypeFunction %void
+        %int = OpTypeInt 32 1
+      %int_0 = OpConstant %int 0
+       %bool = OpTypeBool
+      %false = OpConstantFalse %bool
+      %float = OpTypeFloat 32
+    %v4float = OpTypeVector %float 4
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+ %_GLF_color = OpVariable %_ptr_Output_v4float Output
+    %float_1 = OpConstant %float 1
+    %float_0 = OpConstant %float 0
+         %15 = OpConstantComposite %v4float %float_1 %float_0 %float_0 %float_1
+       %main = OpFunction %void None %5
+         %16 = OpLabel
+               OpSelectionMerge %17 None
+               OpSwitch %int_0 %17 0 %18
+         %18 = OpLabel
+               OpSelectionMerge %19 None
+               OpBranchConditional %false %20 %19
+         %20 = OpLabel
+               OpBranch %19
+         %19 = OpLabel
+               OpBranch %17
+         %17 = OpLabel
+               OpStore %_GLF_color %15
+               OpReturn
+               OpFunctionEnd

test/tint/vk-gl-cts/graphicsfuzz/switch-with-empty-if-false/0.wgsl

@@ -0,0 +1,25 @@
+var<private> x_GLF_color : vec4<f32>;
+
+fn main_1() {
+  switch(0) {
+    case 0: {
+      if (false) {
+      }
+    }
+    default: {
+    }
+  }
+  x_GLF_color = vec4<f32>(1.0, 0.0, 0.0, 1.0);
+  return;
+}
+
+struct main_out {
+  @location(0)
+  x_GLF_color_1 : vec4<f32>;
+};
+
+@stage(fragment)
+fn main() -> main_out {
+  main_1();
+  return main_out(x_GLF_color);
+}