Project Converter: Do not convert lines that start with a comment

[Maran23]

Partially fixes: - #66061
Partially fixes: - #70983

This PR adds detection of lines that start with a comment.
Those lines are ignored so that the text inside the comments remains untouched.
E.g. # Reference is not converted to # RefCounted.
Lines that do not start with a comment, e.g. func _ready(): # Reference will still be converted.

Same applies to C# comments: // Reference

[akien-mga]

Would it be too risky / lead to false positives to make the regex handle inline comments?

At least for GDScript, I think it might be safe to assume that # always starts a comment unless it's:

• In a string (i.e. enclosed with " or two ')
• In a comment (but that doesn't matter I guess)

Might be a bit hard to make fully reliable as strings are messy, so maybe we could just match:

• Lines starting with a comment (this PR)
• Inline comments with no " or ' character after #
  • Would break on words like "it's" but it's maybe better than nothing. Otherwise the regex would need to check for " on both sides of #, with an uneven number of " on the left side, or... I don't know, sounds like a complex problem which should have been solved already for matching comments in Python code :P

[Maran23]

Would it be too risky / lead to false positives to make the regex handle inline comments?

There is a little risk, as you also wrote.
But there is also a little more work involved when converting/overwriting the files.
The logic introduced in this PR is simple: if the line is a comment, it will be ignored during conversion.

If we want to support inline comments, the logic needs to be further improved to separate the line into a code and a comment part.
Then ONLY the code part should be converted and after that both parts should be put back together again.
E.g. func _ready(): # Reference must be tokenized into func _ready(): and # Reference.
Only func _ready(): is converted and then # Reference should be added again.

[akien-mga]

Thanks!

[YuriSizov]

Cherry-picked for 4.0.1.