dex: track outflows in position manager (#5030)

## Describe your changes

Close #5028.

## Checklist before requesting a review

- [x] I have added guiding text to explain how a reviewer should test
these changes.

- [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:

  > Consensus and state breaking

crates/core/component/dex/src/component/position_manager.rs

@@ -18,7 +18,7 @@ use crate::component::{
     dex::StateReadExt as _,
     position_manager::{
         base_liquidity_index::AssetByLiquidityIndex, inventory_index::PositionByInventoryIndex,
-        price_index::PositionByPriceIndex,
+        price_index::PositionByPriceIndex, volume_tracker::PositionVolumeTracker,
     },
 };
 use crate::lp::Reserves;
@@ -518,6 +518,7 @@ trait Inner: StateWrite {
         self.update_trading_pair_position_counter(&prev_state, &new_state)
             .await?;
         self.update_position_by_price_index(&id, &prev_state, &new_state)?;
+        self.update_volume_index(&id, &prev_state, &new_state).await;
 
         self.put(state_key::position_by_id(&id), new_state.clone());
         Ok(new_state)

crates/core/component/dex/src/component/position_manager/volume_tracker.rs

@@ -16,7 +16,7 @@ use penumbra_sdk_sct::component::clock::EpochRead;
 
 #[async_trait]
 pub(crate) trait PositionVolumeTracker: StateWrite {
-    async fn increase_volume_index(
+    async fn update_volume_index(
         &mut self,
         position_id: &position::Id,
         prev_state: &Option<Position>,