feat(app): 🎋 add missing Sct component hooks (#4246)

fixes #3739.

the `App` only ever invokes the Sct component's `init_chain` and
`begin_block` hooks.

this isn't currently a bug, since its `end_block` and `end_epoch` hooks
are noöps, but could easily lead to a surprising outcome in the future,
if more logic was introduced to those trait methods.

#### checklist before requesting a review

- [x] if this code contains consensus-breaking changes, i have added the
"consensus-breaking" label. otherwise, i declare my belief that there
are not consensus-breaking changes, for the following reason:

> while this **does** change the control flow of consensus-critical
logic, this does **not**
change the execution of incoming data. the hooks introduced here are
noöps.

crates/core/app/src/app/mod.rs

@@ -382,6 +382,7 @@ impl App {
 
         tracing::debug!("running app components' `end_block` hooks");
         let mut arc_state_tx = Arc::new(state_tx);
+        Sct::end_block(&mut arc_state_tx, end_block).await;
         ShieldedPool::end_block(&mut arc_state_tx, end_block).await;
         Distributions::end_block(&mut arc_state_tx, end_block).await;
         Ibc::end_block(&mut arc_state_tx, end_block).await;
@@ -485,6 +486,9 @@ impl App {
 
             let mut arc_state_tx = Arc::new(state_tx);
 
+            Sct::end_epoch(&mut arc_state_tx)
+                .await
+                .expect("able to call end_epoch on Sct component");
             Distributions::end_epoch(&mut arc_state_tx)
                 .await
                 .expect("able to call end_epoch on Distributions component");