fix(line): render Line::styled correctly inside a paragraph

[m4rch3n1ng]

rendering a Paragraph with a Line::styled ignores the style, but using styled spans with a Line::default().spans(vec![Span::styled]) works just fine.

the issue seems to be, that the paragraph tries to render the styled_graphemes of the Spans instead of the Line directly

repro of the problem

fn ui(frame: &mut Frame) {
	let l1 = Line::styled("should be bold", Style::default().bold());
	let l2 = Line::styled("should be colorful", Style::default().cyan());
	let l3 = Line::styled("should be dim", Style::default().dim());

	let lp = Line::default();

	let s1 = vec![Span::styled("but it works with spans", Style::default().cyan())];
	let ls = Line::default().spans(s1);

	let block = Block::default()
		.borders(Borders::ALL)
		.padding(Padding::new(4, 4, 2, 2));
	let paragraph = Paragraph::new(vec![l1, l2, l3, lp, ls]).block(block);

	frame.render_widget(paragraph, frame.size());
}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c3fb258) 92.0% compared to head (f35e86f) 92.0%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #930   +/-   ##
=====================================
  Coverage   92.0%   92.0%           
=====================================
  Files         61      61           
  Lines      15521   15551   +30     
=====================================
+ Hits       14286   14316   +30     
  Misses      1235    1235           

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[kdheepak]

Thanks for making a PR! Can you add a test to make sure this fixes it?

[m4rch3n1ng]

done, idk what's going on with codecov though

[joshka]

I think at some point we'll change this to style the entire line and not just the area covered by the spans, but this is fine as a bug fix.