Keep code after a single-line comment before do or after (

[ybai08]

Fixes #1176.

Both cases in the issue produced output that no longer parses, because a single-line comment ended up in front of code on the same line.

1. Numeric for with a comment before do. format_numeric_for always appended " do" after the end or step expression, so a trailing -- comment on that expression swallowed it. If the last expression of the header (the step, or else the end) has a trailing single-line comment, or do has a leading one, it now ends that expression with a newline and puts do on its own line, with do's leading comments handled as while does (format_end_token, IndentComments). while and generic for already keep do on its own line in this case. A block comment (--[[ ]]) before do is unchanged, since it can't swallow anything.

2. Comment right after ( in a hanging condition. In format_hanging_expression_, a short parenthesised expression took the single-line shortcut when the expression itself had no comments. A comment attached to the opening parenthesis wasn't checked, so ( -- comment was followed by b or c) on the same line. A trailing single-line comment on ( now sends it down the existing hanging path, which already puts the expression on the next line.

Output for the issue's inputs:

for i = 1, 2 -- comment
do
	print(i)
end

if
	a and ( -- comment
		b or c
	)
then
	print("yes")
end

The second fix also covers local x = ( -- comment followed by 1 + 2 ), which on main gave local x = ( -- comment1 + 2).

Tests

There are two new snapshot inputs.

tests/inputs/numeric-for-comment-before-do.lua covers:

• the issue's case;
• the same with a step;
• a comment on its own line before do;
• a block comment before do, which stays on one line.

tests/inputs/parentheses-comment-after-open.lua covers the issue's condition and the local case.

Without the two src changes, both snapshots fail. With them, cargo test passes for every feature set in ci.yml on macOS arm64:

Features	Passed
default	201
--no-default-features	144
luau	210
lua52	203
lua53	204
lua54	205
luajit	203
cfxlua	206

Formatting the new snapshots' output again gives the same output, and it parses. cargo fmt --check and cargo clippy --all-targets --all-features are clean.

A related case I left alone: print(( -- c / 1 / )) drops the comment on main and still does with this change. The redundant inner parentheses are removed along with the comment attached to them. That's a different code path, so I can open a separate issue if you like.