profiles/internal: Add ServesLeaf/IsLeaf to the Endpoint

This is the second part of
https://vanadium-review.googlesource.com/#/c/8596/

With this change, the naming.Endpoint now shows 'l' instead of 's' when
the server is a leaf dispatcher.

MultiPart: 2/2
Change-Id: I6ddd54907bcacfaf9e81356164917f2b391e631c
5 files changed