improve performance of route generation (#914)

this may fix following problem:

1. cpu 100% when large number of nodes in network.
2. high cpu usage when large number of foreign networks.
3. packet loss when new node enters/exits.
4. old routes not cleand and show as an obloleted entry.

easytier/Cargo.toml

@@ -138,6 +138,7 @@ network-interface = "2.0"
 
 # for ospf route
 petgraph = "0.8.1"
+hashbrown = "0.15.3"
 
 # for wireguard
 boringtun = { package = "boringtun-easytier", version = "0.6.1", optional = true }