UX improvements in the new user menu

[bryanboza]

We need some UX work here:

We are adding a distinction for the default site with a check mark, which is confusing because from sites portlet to set a default we are using another icon.

Also, when you have multiple sites and you select some one specific, when you open again the site selector we are displaying the selected in letter. For me the selected should be the one with the checkmark and in bold, and we need to use the default icon for distinction of the default one.

@melissarojas-dotcms maybe you can help here.

Originally posted by @bryanboza in https://github.com/dotCMS/core/issues/25743#issuecomment-1861804183