Add a chevronSize parameter for the BreadcrumbBar widget

[Raafa19]

Is your feature request related to a problem? Please describe.
Hi, when it comes to using the BreadcrumbBar widget, in places where the text size is different than the default (example: PageHeader), the chevron icon size remains 8px. It looks kinda weird.

Describe the solution you'd like
Little modification to the BreadcrumbBar widget, adding a chevronSize parameter.

Describe alternatives you've considered
The next would be the implementation:

  /// Size of the chevron icon
  final double? chevronSize;

  /// Creates a breadcrumb bar.
  const BreadcrumbBar({
    super.key,
    required this.items,
    this.chevronSize,
    this.overflowButtonBuilder = _defaultOverflowButtonBuilder,
    this.onItemPressed,
  });

The chevron widget:

final chevron = Padding(
      padding: const EdgeInsetsDirectional.symmetric(horizontal: 6.0),
      child: Icon(
        textDirection == TextDirection.ltr
            ? FluentIcons.chevron_right
            : FluentIcons.chevron_left,
        size: widget.chevronSize ?? 8.0,
        color: theme.resources.textFillColorPrimary,
      ),
    );

Additional context
Example header (default 8px)

Example header (12px)

The same argument could be said to the more icon, but it doesn't seem necessary.

[bdlukaa]

I think we can automatically adjust the icon size according to the text font size.

The default icon size in the native implementation is 12.
https://github.com/microsoft/microsoft-ui-xaml/blob/aeed4c19e2fc7c2c093216a51b651f2f0890c930/src/controls/dev/Breadcrumb/BreadcrumbBar_themeresources.xaml#L33