Allow dead_code in all metric structs

Issue is being tracked in
<rust-lang/rust#88900>. Basically the
dead_code lint was changed to ignore derive fmt::Debug implementations,
generally a good thing, but the metrics are only written to and then
printed using the (derived) fmt::Debug implementations so they are
actually read.

src/rt/coordinator.rs

@@ -46,6 +46,7 @@ pub(super) struct Coordinator {
 
 /// Metrics for [`Coordinator`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 struct Metrics<'c, 'l> {
     heph_version: &'static str,
     os: &'c str,

src/rt/local/mod.rs

@@ -713,6 +713,7 @@ pub(super) struct RuntimeInternals {
 
 /// Metrics for [`RuntimeInternals`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct Metrics {
     id: NonZeroUsize,
     scheduler: scheduler::Metrics,

src/rt/local/scheduler/mod.rs

@@ -36,6 +36,7 @@ pub(crate) struct Scheduler {
 
 /// Metrics for [`Scheduler`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct Metrics {
     ready: usize,
     inactive: usize,

src/rt/local/timers.rs

@@ -81,6 +81,7 @@ pub(crate) struct Timers {
 
 /// Metrics for [`Timers`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct Metrics {
     timers: usize,
     next_timer: Option<Duration>,

src/rt/shared/mod.rs

@@ -98,6 +98,7 @@ pub(crate) struct RuntimeInternals {
 
 /// Metrics for [`RuntimeInternals`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct Metrics {
     scheduler: scheduler::Metrics,
     timers: timers::Metrics,

src/rt/shared/scheduler/mod.rs

@@ -104,6 +104,7 @@ pub(super) struct Scheduler {
 
 /// Metrics for [`Scheduler`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct Metrics {
     ready: usize,
     inactive: usize,

src/rt/shared/timers.rs

@@ -89,6 +89,7 @@ struct Epoch {
 
 /// Metrics for [`Timers`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct Metrics {
     timers: usize,
     next_timer: Option<Duration>,

src/trace.rs

@@ -169,6 +169,7 @@ pub(crate) struct CoordinatorLog {
 
 /// Metrics for [`CoordinatorLog`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct CoordinatorMetrics<'l> {
     file: &'l File,
     counter: u32,
@@ -266,6 +267,7 @@ pub(crate) struct Log {
 
 /// Metrics for [`Log`].
 #[derive(Debug)]
+#[allow(dead_code)] // https://github.com/rust-lang/rust/issues/88900.
 pub(crate) struct Metrics {
     counter: u32,
 }