Add a fuzz target to test monitor update failure handling

Author: TheBlueMatt

fuzz/Cargo.toml

@@ -44,6 +44,10 @@ path = "fuzz_targets/peer_crypt_target.rs"
 name = "full_stack_target"
 path = "fuzz_targets/full_stack_target.rs"
 
+[[bin]]
+name = "chanmon_fail_consistency"
+path = "fuzz_targets/chanmon_fail_consistency.rs"
+
 [[bin]]
 name = "router_target"
 path = "fuzz_targets/router_target.rs"