Consider changes to code style inspired by review of PHP Parser test fixtures

[lkrms]

• [ ] Don't move comments to the other side of empty statements?

• [ ] Relax enforcement of class attributes on their own line when the class is a one-line and/or anonymous class?

• [ ] Expand this

  <?php
  [
      $foo,,,
      $bar,
      $baz,
  ] = $data;
  

  to this?

  <?php
  [
      $foo,
      ,
      ,
      $bar,
      $baz,
  ] = $data;
  

• [ ] Improve tag indentation in this scenario:

  <?php
  function test() {
      ?>
  Test
      <?php
  }
  

• [x] ~~Suppress .0 in floats with an exponent, e.g. 3.0e5?~~

• [x] Remove leading space from & in fn &() => null for consistency with fn() => null

• [x] Check formatting of declare blocks without braces

• [x] Review switch indentation? e.g.

  <?php
  switch ($a) {
      case 0:
          break;
          // Deindent this after `break`/`return`/`throw`?
      case 1:
      default:
          break;
  }
  

• [x] Handle leading semicolons in switches

  <?php
  switch ($a) {
          ;
  }