Fix crash caused by trailing spaces

[JulianHeuser]

Fixes #103797
Issue introduced in #101319

(Also is mildly more efficient since it isn't redundantly splitting twice)

[tdaven]

I can confirm that this fixes #103797 for me.

[dalexeev]

Suggested change

	Vector<String> str_stripped_split = str.strip_edges().split_spaces();
	if (!str_stripped_split.is_empty() &&
	str_stripped_split[0] != "#region" &&
	str_stripped_split[0] != "#endregion") {
	match = false;
	}
	String stripped_str = str.strip_edges();
	if (!stripped_str.begins_with("#region") && !stripped_str.begins_with("#endregion")) {
	match = false;
	}

[JulianHeuser]

This works but undoes the original fix where this bug was introduced.
For example, "#region" and "#endregion" here are highlighted, but don't actually create a region you can collapse or expand.

We need to check for whitespace after region/endregion to fix this.

To improve this code's efficiency, it would be nice if get_spaces had a maxsplit parameter like the normal split function does, but I don't know if its worth adding that extra functionality just for this.

[dalexeev]

Yes, we can use the maxsplit parameter since we are only checking the 0th substring.

Or alternatively we could extract the alphanumeric identifier after the #. Since the current version does not take into account cases like #region:Name. I think we should add methods like String.get_{ascii,unicode}_identifier(from: int = 0) -> String.

[JulianHeuser]

Is there a source for what characters should be after #region or is that up in the air? The only examples the docs show are with whitespace.