Remove UniqueId.SerializedForm

[mpkorstanje]

With #5205 UniqueId.uniqueIdFormat was removed. To preserve backwards compatibility w.r.t to serialization a UniqueId.SerializedForm was added. This can be removed on the next major release.

Deliverables

• Remove UniqueId.SerializedForm
• Make UniqueId.segments actually final
• Remove custom writeObject and readObject methods.