GLSL: clean up GLSL output whitespace generation.

More line() and less std::endl.
More automated indents and less manual spacing.
Put a single newline after every struct and function declaration.

Note that this does touch every test result, but only affects whitespace.

Change-Id: I7506b9029b79b91fb335911dba44369b36f09bbe
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/78300
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

test/buffer/uniform/dynamic_index/read.wgsl.expected.glsl

@@ -14,6 +14,7 @@ struct Inner {
   mat3x2 j;
   ivec4 k[4];
 };
+
 struct S {
   Inner arr[8];
 };
@@ -45,10 +46,11 @@ void tint_symbol(tint_symbol_2 tint_symbol_1) {
   tint_symbol_inner(tint_symbol_1.idx);
   return;
 }
+
+
 void main() {
   tint_symbol_2 inputs;
   inputs.idx = uint(gl_LocalInvocationIndex);
   tint_symbol(inputs);
 }
 
-