DSLX formatter removes comments around proc channel declarations

[mikex-oss]

Describe the bug After running through dslx autofmt, the comments describing a channel declaration are gone.

To Reproduce Steps to reproduce the behavior:

1. Take the example adder proc in the proc tutorial and add comments above each channel declaration.

pub proc adder {
  // foo
  A: chan<u32> in;
  // bar
  B: chan<u32> in;
  // baz
  C: chan<u32> out;

2. Run the formatter or dslx_fmt_test.
3. You will see the comments removed; test diff shown below:

<   // foo
<   A: chan<u32> in;
<   // bar
<   B: chan<u32> in;
<   // baz
<   C: chan<u32> out;
---
>     A: chan<u32> in;
>     B: chan<u32> in;
>     C: chan<u32> out;

Expected behavior Comments should be preserved.

[mikex-oss]

Note inline comments and blank lines (between comment and declaration, or between declarations) doesn't seem to workaround this issue.

[cdleary]

We think this should be fixed by #1535