build: Correctly enable dhat support in vmm crate

The "dhat-heap" feature needs to be enabled inside the vmm crate as a
depenency from the top-level as there is build time check for that
feature inside the vmm crate.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

Cargo.toml

@@ -63,7 +63,7 @@ wait-timeout = "0.2.0"
 [features]
 default = ["kvm", "io_uring"]
 dbus_api = ["zbus", "vmm/dbus_api"]
-dhat-heap = ["dhat"] # For heap profiling
+dhat-heap = ["dhat", "vmm/dhat-heap"] # For heap profiling
 guest_debug = ["vmm/guest_debug"]
 igvm = ["vmm/igvm", "mshv"]
 io_uring = ["vmm/io_uring"]