decouple the storage logic from Node object

Summary:
Similar to `Network` struct, there will `Storage` comprising all information about block devices with a concrete lifetime.

Ref:
https://www.internalfb.com/code/fbsource/%5Bf622b7d63124%5D%5Bhistory%5D/fbcode/host_management/service_configs/libcfgen/rust/src/hw/network.rs?lines=5-8

Reviewed By: anps77

Differential Revision: D57781337

fbshipit-source-id: cf248df0b776ba9da421a3c4c3bddefbb3ae938a

src/oomd/cfgen/src/cfgen.rs

@@ -730,7 +730,7 @@ fn oomd2_oomd_restart_threshold() -> BTreeMap<String, OomdRestartThreshold> {
 }
 
 fn on_ssd(node: &Node) -> bool {
-    node.has_ssd_root()
+    node.storage().has_ssd_root()
 }
 
 fn io_latency_supported(_node: &Node) -> bool {