Change Id format

[akiradeveloper]

Raft node can be identified by its address because it is unique. This is why lol defines Id = Address.

My idea is change this to Id = (Label, Address). This change will make it easy to

1. Read the log: If address is used as Id in the log, it is difficult to read. If it is shorter like "ND1", it will become easy to identify.
2. Match different Ids: You may make a Raft cluster on k8s. How to match Pod's label and lol's node? If we use the same label in both layers, matching becomes easy.

Also, as the label is shorter than Address it is much efficient to compare two labels instead of addresses. This will be a bit of optimization.

[akiradeveloper]

If we do Multi-Raft #131 we should add raft-group-id to the log like

ND1(gid=3): Send RPC to ND5(gid=3)

This should be also considered.

[akiradeveloper]

idea:

• Id will be changed to (Id, Url) where Id is unique u64. (Uniqueness is guaranteed by the admin)
• In initialization, we set only (Id).
• In AddServer, we give (Id, Url) so receiver can get binding Id -> Url.
• In RemoveServer, we give (Id) so receiver can remove binding Id -> Url if exists.
• The log format wil be change to "ND{Id}> xxxx".

[akiradeveloper]

Just to avoid deep copy, some library is making such effort. https://sixtyfps.io/releases/0.1.1/docs/rust/sixtyfps/struct.sharedstring