chore(easytier): gate hotpath-rs 0.19 dependency and off-mode shim

Re-enable the hotpath profiler as an optional dependency gated behind the
 feature (default off). In off builds the crate stays out of the
dependency graph entirely:  plus a local
 module provide no-op // macros so
call sites compile unchanged. Also add a  guarding the
mutual exclusivity of  with the / global
allocators.

easytier/Cargo.toml

@@ -58,6 +58,8 @@ chrono = { version = "0.4.37", features = ["serde"] }
 guarden = "0.2"
 quanta = "0.12"
 
+hotpath = { version = "0.19", default-features = false, optional = true }
+
 delegate = "0.13.5"
 
 itertools = "0.14.0"
@@ -410,11 +412,14 @@ tracing = ["tokio/tracing", "dep:console-subscriber"]
 magic-dns = ["dep:hickory-client", "dep:hickory-server"]
 faketcp = ["dep:flume"]
 zstd = ["dep:zstd"]
-# Deprecated: hotpath profiling has been removed. These feature aliases are
-# retained as no-ops so existing build scripts using `--features hotpath*`
-# continue to work without pulling in any dependencies.
-hotpath = []
-hotpath-cpu = ["hotpath"]
-hotpath-alloc = ["hotpath"]
+hotpath = [
+    "dep:hotpath",
+    "hotpath/hotpath",
+    "hotpath/tokio",
+    "hotpath/parking_lot",
+    "hotpath/flume",
+]
+hotpath-cpu = ["hotpath", "hotpath/hotpath-cpu"]
+hotpath-alloc = ["hotpath", "hotpath/hotpath-alloc"]
 # For Network Extension on macOS
 macos-ne = []