fix: a lot of instances of clippy::needless_lifetimes

Summary:
This doesn't get all of them because:
1. there are so many of them
2. the lint is pretty jank

Part of facebook/buck2#943

X-link: facebook/buck2#944

Reviewed By: JakobDegen

Differential Revision: D74271655

Pulled By: dtolnay

fbshipit-source-id: c7e41c47248d4be1f5d33a14b676ab35fc5180e2

Author: lf-

allocative/src/flamegraph.rs

@@ -137,7 +137,7 @@ struct TreeRef<'a> {
     tree_id: TreeId,
 }
 
-impl<'a> TreeRef<'a> {
+impl TreeRef<'_> {
     fn write_flame_graph(&self, stack: &[&str], warnings: &mut String) -> FlameGraph {
         let mut flame_graph = FlameGraph::default();
         let tree = &self.trees[self.tree_id];
@@ -240,7 +240,7 @@ struct TreeStackRef<'t, 's> {
     stack: &'s mut TreeStack,
 }
 
-impl<'t, 's> TreeStackRef<'t, 's> {
+impl<'t> TreeStackRef<'t, '_> {
     fn current_data(&'t mut self) -> &'t mut TreeData {
         &mut self.trees[self.stack.tree]
     }

allocative/src/visitor.rs

@@ -61,7 +61,7 @@ pub struct Visitor<'a> {
     pub(crate) node_kind: NodeKind,
 }
 
-impl<'a> Drop for Visitor<'a> {
+impl Drop for Visitor<'_> {
     fn drop(&mut self) {
         self.exit_impl();
     }