KtBreadcrumb: Remove or Simplify Separator

[FlorianWendelborn]

Current way is overkill, and the need for it is unclear.

(Via #504 (comment))

[Isokaeder]

In general we either want a slash / or yoco's CHEVRON_RIGHT icon. If we only want one, I would personally favor CHEVRON_RIGHT. So we can either always use that or at least use an enum like this as prop instead of current madness:

enum Separator {
  SLASH, CHEVRON_RIGHT
}

Personally would choose Occam's Razor aprroach and just use CHEVRON_RIGHT though.