feat: show full type in tooltips for hints

[roife]

fix #19615.

[roife]

[roife]

Previously, hovering over any part of a hint would display the complete type.

Now, the certain hidden content is only showed when the mouse hovers over its corresponding ....

[Veykril]

I'd expect something like the following instead

Suggested change

	fn maybe_truncated<T, F: FnOnce(&mut Self) -> T>(&mut self, f: F) -> T {
	let truncated = self.should_truncate() && self.fmt.start_truncated();
	let res = f(self);
	if truncated {
	self.fmt.end_truncated();
	}
	res
	}
	fn maybe_truncated<T, F: FnOnce(&mut Self) -> T>(&mut self, f: F) -> Option<T> {
	if self.should_truncate() {
	let end_truncate = self.fmt.start_truncated();
	if self.fmt.start_truncated() {
	let res = f(self);
	self.end_truncated();
	Some(res)
	} else {
	write!(self, "{TYPE_HINT_TRUNCATION}")
	None
	}
	} else {
	Some(f(self))
	}
	}

This way any writers that don't care about the truncation behavior will have the previous behavior, that is they write the truncation dots as before.

[roife]

When self.fmt.start_truncated() returns false, we should call f(self) to write the type into last_part instead of writing .... A false return value indicates that the last part is a truncated part, and its content will be displayed in the tooltip. Therefore, we should write the complete value directly rather than truncating it.

For example, in SSSS<...>, if the ... represents a long type like TTTT<i32>, should_truncated will be true, but we should write the full signature TTTT<i32> into the last part (so that the tooltip shows TTTT<i32>) instead of just writing TTTT<...>.

[Veykril]

Suggested change

	in_truncated = !in_truncated && self.should_truncate() && self.fmt.start_truncated();
	if self.should_truncate() {
	in_truncated |= !in_truncated && self.fmt.start_truncated();
	if !in_truncated {
	return write!(self, "{TYPE_HINT_TRUNCATION}");
	}
	}

same reason as the review above