feat: subnet activity rollups and validator rewards (phase 1)

Cargo.toml

@@ -36,6 +36,7 @@ members = [
   "fendermint/actors",
   "fendermint/actors/api",
   "fendermint/actors/chainmetadata",
+  "fendermint/actors/activity-tracker",
   "fendermint/actors/eam",
   "fendermint/actors/gas_market/eip1559",
 ]
@@ -222,6 +223,7 @@ fil_actor_eam = { git = "https://github.com/filecoin-project/builtin-actors", ta
 fil_actors_runtime = { git = "https://github.com/filecoin-project/builtin-actors", tag = "v15.0.0" }
 
 fendermint_actor_eam = { path = "./fendermint/actors/eam" }
+fendermint_actor_activity_tracker= { path = "./fendermint/actors/activity-tracker" }
 
 cid = { version = "0.10.1", default-features = false, features = [
   "serde-codec",