new_reception_timestamp() should be method of session

[milyin]

Describe the release item

new_reception_timestamp() is somehow weird since ZenohId is always set to 1. To be verified wether should become a method of the session and be called new_timestamp().

[milyin]

it's inconvenient to put it into session. All what is needed from session is session's id. This will require store pointer to session, although the copy of session id would be enough. This is the case for Snapshotter structure: https://github.com/eclipse-zenoh/zenoh/blob/main/plugins/zenoh-plugin-storage-manager/src/replica/snapshotter.rs#L28