[refmt] Comment on first argument does not stay attached to argument after reformat

Reason try link, then click refmt in top right

Before:

let fn =
    (
      /* Comment about argument 1 */
      longArgumentName1,
      longArgumentName2,
      longArgumentName3,
      longArgumentName4,
      longArgumentName5,
      longArgumentName6,
      longArgumentName7,
      longArgumentName8,
      longArgumentName9,
      longArgumentName10,
      longArgumentName11,
      longArgumentName12
    ) =>
  ();

Actual after refmt:

let fn =
    /* Comment about argument 1 */
    (
      longArgumentName1,
      longArgumentName2,
      longArgumentName3,
      longArgumentName4,
      longArgumentName5,
      longArgumentName6,
      longArgumentName7,
      longArgumentName8,
      longArgumentName9,
      longArgumentName10,
      longArgumentName11,
      longArgumentName12
    ) =>
  ();

Expected after refmt:

let fn =
    (
      /* Comment about argument 1 */
      longArgumentName1,
      longArgumentName2,
      longArgumentName3,
      longArgumentName4,
      longArgumentName5,
      longArgumentName6,
      longArgumentName7,
      longArgumentName8,
      longArgumentName9,
      longArgumentName10,
      longArgumentName11,
      longArgumentName12
    ) =>
  ();

Reproduce the example from the linked Reason Try page by clicking refmt and compare the before, actual, and expected output shown in the issue. Trace the refmt formatting entry point and comment handling for function arguments, then add a regression test covering this example. Done means the comment remains immediately before longArgumentName1 after formatting.