Indent according to parent depth, even with trailing text

Previously we had custom logic to handle hanging arguments.

    foo($x,
        $y);

This was getting confused by other forms of trailing text after
parens:

    if (true) { // hello
      foo();
    }

foo() should not line up with { here.

This heuristic isn't useful, because hackfmt only uses the following
two forms:

    foo($x, $y);
    // or
    foo(
      $x,
      $y,
    );

Remove this heuristic. This also solves most of #29.

hack-mode.el

@@ -1720,14 +1720,6 @@ Preserves point position in the line where possible."
          (paren-depth (hack--paren-depth-for-indent (line-beginning-position)))
 
          (ppss (syntax-ppss (line-beginning-position)))
-         (current-paren-pos (nth 1 ppss))
-         (text-after-paren
-          (when current-paren-pos
-            (save-excursion
-              (goto-char current-paren-pos)
-              (buffer-substring
-               (1+ current-paren-pos)
-               (line-end-position)))))
          (in-multiline-comment-p (nth 4 ppss))
          (current-line (hack--current-line)))
     ;; If the current line is just a closing paren, unindent by one level.
@@ -1749,18 +1741,6 @@ Preserves point position in the line where possible."
       (when (or (string-match-p (rx bol (0+ space) "*") current-line)
                 (string= "" current-line))
         (hack--indent-preserve-point (1+ (* hack-indent-offset paren-depth)))))
-     ;; Indent according to the last paren position, if there is text
-     ;; after the paren. For example:
-     ;; foo(bar,
-     ;;     baz, <- this line
-     ((and
-       text-after-paren
-       (not (string-match-p (rx bol (0+ space) eol) text-after-paren)))
-      (let (open-paren-column)
-        (save-excursion
-          (goto-char current-paren-pos)
-          (setq open-paren-column (current-column)))
-        (hack--indent-preserve-point (1+ open-paren-column))))
      ;; Indent according to the amount of nesting.
      (t
       (let ((current-line (s-trim current-line))

test/hack-unit-test.el

@@ -229,6 +229,17 @@ $foo
       (indent-region (point-min) (point-max))
       (should (string= (buffer-string) src)))))
 
+(ert-deftest hack-indent-trailing-comment ()
+  (let ((src "function foo(): void { // stuff
+  bar();
+}"))
+    (with-temp-buffer
+      (hack-mode)
+      (insert src)
+
+      (indent-region (point-min) (point-max))
+      (should (string= (buffer-string) src)))))
+
 (ert-deftest hack-indent-xhp ()
   "Ensure we indent XHP expressions correctly."
   (let ((src "<?hh