Clippy lints for rust 1.66 (#3810)

## Issue Addressed
Fixes the new clippy lints for rust 1.66

## Proposed Changes

Most of the changes come from:
- [unnecessary_cast](https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast)
- [iter_kv_map](https://rust-lang.github.io/rust-clippy/master/index.html#iter_kv_map)
- [needless_borrow](https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow)

## Additional Info

na

validator_client/src/key_cache.rs

@@ -104,7 +104,7 @@ impl KeyCache {
         let file = File::options()
             .read(true)
             .create_new(false)
-            .open(&cache_path)
+            .open(cache_path)
             .map_err(Error::UnableToOpenFile)?;
         serde_json::from_reader(file).map_err(Error::UnableToParseFile)
     }