chore: Fix nightly lints (#12746)

- Remove some unused code
- Use `is_multiple_of()` instead of '%'
- Collapse consecuative "if let" statements
- Elided lifetime fixes

It is enough just to review the code of your team

proxy/src/metrics.rs

@@ -553,14 +553,6 @@ impl From<bool> for Bool {
     }
 }
 
-#[derive(LabelGroup)]
-#[label(set = InvalidEndpointsSet)]
-pub struct InvalidEndpointsGroup {
-    pub protocol: Protocol,
-    pub rejected: Bool,
-    pub outcome: ConnectOutcome,
-}
-
 #[derive(LabelGroup)]
 #[label(set = RetriesMetricSet)]
 pub struct RetriesMetricGroup {

proxy/src/stream.rs

@@ -102,7 +102,7 @@ pub struct ReportedError {
 }
 
 impl ReportedError {
-    pub fn new(e: (impl UserFacingError + Into<anyhow::Error>)) -> Self {
+    pub fn new(e: impl UserFacingError + Into<anyhow::Error>) -> Self {
         let error_kind = e.get_error_kind();
         Self {
             source: e.into(),