[JENKINS-75851] Enhance breadcrumb with visual indication to show that there are dropdowns #16774

Add visual aids to indicate that the links will trigger dropdown menus. The problem with the current implementation is that there is no way to know that the breadcrumb will trigger a dropdown which is bad UX and as well bad  accessibility (a11y). 

 

https://www.a11y-collective.com/blog/mastering-web-accessibility-making-drop-down-menus-user-friendly/

> It’s not enough to make drop-down menus and submenus function well. They need to be user-friendly and accessible, especially for individuals with disabilities. They should be clearly indicated to the user.
Visually, this can be done through design elements. Icons such as downward arrows, rightward arrows, or chevrons next to menu items represent the presence of additional options. This can be further complemented by text style alterations, such as underlining the text of the menu items or making them bold.