fix(autofmt): remove extra whitespace before commas in for-loop tuple patterns (#5384)

* fix(autofmt): remove extra whitespace before commas in for-loop tuple patterns

`dx fmt` was adding spaces before commas in for-loop destructuring
patterns (e.g. `for (index , name , value)`) because `TokenStream::Display`
inserts spaces between every token. Route the pattern through prettyplease
via a new `unparse_pat` helper, following the existing `unparse_expr` pattern.

Fixes #5348

* style: apply rustfmt to writer.rs

---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

packages/autofmt/tests/samples.rs

@@ -64,4 +64,5 @@ twoway![
     expr_on_conditional,
     blank_lines,
     blank_lines_preserved,
+    forloop_tuple,
 ];