feat: add optional hotpath profiling support (#2380)

* feat: add hotpath profiling support
* perf(hotpath): make hotpath an optional dependency

easytier/src/lib.rs

@@ -5,6 +5,15 @@ use std::io;
 use clap::Command;
 use clap_complete::{Generator, Shell};
 
+// When the `hotpath` feature is off, alias the current crate as `hotpath` so
+// call sites keep using `hotpath::...` paths, and provide a local no-op shim
+// for the profiling macros. This keeps `hotpath` an optional dependency: the
+// profiler is absent from the dependency graph entirely in default builds.
+#[cfg(not(feature = "hotpath"))]
+extern crate self as hotpath;
+#[cfg(not(feature = "hotpath"))]
+mod hotpath_off;
+
 mod arch;
 mod gateway;
 pub mod instance;