writer/hlsl: Fix continuing block emission

Inline the `continuing` block in the places where `continue` is called.

Simplifies the emission, and fixes emission of `let` statements in the loop.

Also fix random indenting of intrinsic functions.

Fixed: tint:744
Fixed: tint:818
Change-Id: I06994dbc724bc646e0435a1035b00760eaf5f5ab
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51784
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

test/ptr_ref/load/local/ptr_function.wgsl.expected.hlsl

@@ -1 +1,7 @@
-SKIP: Failed to generate: error: pointers not supported in HLSL
+[numthreads(1, 1, 1)]
+void main() {
+  int i = 123;
+  const int use = (i + 1);
+  return;
+}
+

test/ptr_ref/load/local/ptr_private.wgsl.expected.hlsl

@@ -1 +1,8 @@
-SKIP: Failed to generate: error: pointers not supported in HLSL
+static int i = 123;
+
+[numthreads(1, 1, 1)]
+void main() {
+  const int use = (i + 1);
+  return;
+}
+

test/ptr_ref/load/local/ptr_uniform.wgsl.expected.hlsl

@@ -1 +1,12 @@
-SKIP: Failed to generate: error: pointers not supported in HLSL
+struct S {
+  int a;
+};
+
+ConstantBuffer<S> v : register(b0, space0);
+
+[numthreads(1, 1, 1)]
+void main() {
+  const int use = (v.a + 1);
+  return;
+}
+

test/ptr_ref/load/local/ptr_workgroup.wgsl.expected.hlsl

@@ -1 +1,9 @@
-SKIP: Failed to generate: error: pointers not supported in HLSL
+groupshared int i;
+
+[numthreads(1, 1, 1)]
+void main() {
+  i = 123;
+  const int use = (i + 1);
+  return;
+}
+