feat: Port missing IsoTpBehaviour flags

[skullim]

Extends https://github.com/marcelbuesing/socketcan-isotp/pull/11/commits by adding additional flags.

• Added support for setting functional addressing by exposing the necessary ISO-TP socket flags.
• Extended the API to allow enabling individual flags without overwriting existing ones.
• Performed small refactorings to decouple socket construction steps. The initial goal was to define a public API for opening broadcast sockets, but that turned out unnecessary. These changes can be reverted if preferred.