chore: cargo lint

Satisfies the latest cargo lints. I took the easy way out, preserving
the existing function sigs, rather than performing a deeper refactor.

Revert "ci: disable -D warnings"
This reverts commit 4e7c77b.

Closes #3543.

.github/workflows/rust.yml

@@ -15,13 +15,12 @@ jobs:
         uses: taiki-e/install-action@nextest
       - name: Load rust cache
         uses: astriaorg/[email protected]
-      - name: Run cargo check
+      - name: Run cargo check, failing on warnings
         run: cargo check --release
         env:
           # The `-D warnings` option causes an error on warnings;
-          # but it caused apparently spurious warnings, so it was disabled.
           # we must duplicate the rustflags from `.cargo/config.toml`.
-          RUSTFLAGS: "--cfg tokio_unstable"
+          RUSTFLAGS: "-D warnings --cfg tokio_unstable"
 
       # If a dependency was modified, Cargo.lock may flap if not committed.
       - name: Check for diffs

crates/bin/pcli/src/command/ceremony.rs

@@ -22,7 +22,7 @@ use penumbra_proto::{
     view::v1alpha1::GasPricesRequest,
 };
 use penumbra_transaction::memo::MemoPlaintext;
-use penumbra_view::{Planner, ViewClient};
+use penumbra_view::Planner;
 
 use crate::App;
 

crates/bin/pcli/src/command/view/balance.rs

@@ -17,7 +17,7 @@ impl BalanceCmd {
         false
     }
 
-    pub async fn exec<V: ViewClient>(&self, fvk: &FullViewingKey, view: &mut V) -> Result<()> {
+    pub async fn exec<V: ViewClient>(&self, _fvk: &FullViewingKey, view: &mut V) -> Result<()> {
         let asset_cache = view.assets().await?;
 
         // Initialize the table

crates/bin/pcli/src/command/view/staked.rs

@@ -23,7 +23,7 @@ impl StakedCmd {
 
     pub async fn exec(
         &self,
-        full_viewing_key: &FullViewingKey,
+        _full_viewing_key: &FullViewingKey,
         view_client: &mut impl ViewClient,
         pd_channel: Channel,
     ) -> Result<()> {