[dev/1.0.0]Fix EntityGlobalId

[wyfo]

Describe the release item

There is no current way to have a EntityGlobalId corresponding to a Session, so it's not possible to have a SourceInfo corresponding to a Session.
As discussed with @OlivierHecart, Session should have an EntityId, which may be 0, or not in the case of multiple session sharing a same runtime (e.g. plugins).

Also, according to @OlivierHecart, we may want Reply::replier_id to be an EntityGlobalId instead of a ZenohId.

@Mallets @milyin What do you think?

[Mallets]

I think the proposal makes sense. +1

[milyin]

replier_id is declared unstable now, so this issue is not a priority. Source info is unstable too
#709