Block title_style is not rendered

[joshka]

Description

In the recent PR to support multiple titles, we accidentally made title_style no longer effective. It's useful to have this as a fallback style as it makes it easy to apply a style to all titles except one:
e.g.

Block::new()
  .title_style(Style::new().bold())
  .title(Title::from("foo").alignment(Alignment::Left))
  .title(Title::from("bar").alignment(Alignment::Center))
  .title(Title::from("foo".not_bold().dim()).alignment(Alignment::Right))

To Reproduce

    frame.render_widget(
        Block::new()
            .borders(Borders::all())
            .title("Styled Title")
            .title_style(Style::new().yellow()),
        area1,
    );
    frame.render_widget(
        Block::new()
            .borders(Borders::all())
            .title(Title::from(Line::styled(
                "Styled Line",
                Style::new().yellow(),
            ))),
        area 2,
    );

Expected behavior

The Block's title style should be applied to the title.
The order which styles should effect the title (later styles should override earlier):

1. Any style applied to the surrounding area
2. Block.style
3. Block.border_style
4. Block.title_style - this is the missing piece
5. Title.content.style (Line.style): Out of scope for this issue as Line currently doesn't have a style, but should
6. Title.content.spans -> Span.style

Screenshots

Environment

• OS: Mac
• Terminal Emulator: iterm2
• Font: FiraCode NF
• Crate version: 0.22
• Backend: crossterm

Additional context

This is the code that needs to be modified for this:

ratatui/src/widgets/block.rs

Lines 418 to 423 in bf49446

	buf.set_line(
	title_x + area.left(),
	self.get_title_y(position, area),
	&title.content,
	title_area_width,
	);

ratatui/src/widgets/block.rs

Lines 444 to 449 in bf49446

	buf.set_line(
	title_x + area.left(),
	self.get_title_y(position, area),
	&title.content,
	title_area_width,
	);

ratatui/src/widgets/block.rs

Lines 465 to 470 in bf49446

	buf.set_line(
	area.width.saturating_sub(title_x) + area.left(),
	self.get_title_y(position, area),
	&title.content,
	title_area_width,
	);

There's a simple ways to approach this (just create a new line from the old line with the appropriate title_style applied before the line's style).

There's also a more complex fix for this that changes the way line style is stored / rendered so that line style overrides can be consistently handled by any widget. If you decide to implement the complex approach, please implement the simple approach first so there is tests for the intended behavior, and discuss the API changes for this prior to implementation as this likely requires changes to the public api of ratatui.