changelog: add #3472

.changelog/unreleased/improvements/3472-systems-crate.md

@@ -0,0 +1,5 @@
+- Added a new namada_systems crate to contain abstract systems interfaces,
+  previously added to core crate. Also switched to use the concrete
+  storage error and result type instead of the generic associated
+  type which reduces the amount of typing needed one the caller side.
+  ([\#3472](https://github.com/anoma/namada/pull/3472))