proxy: format imports with nightly rustfmt (#9414)

```shell
cargo +nightly fmt -p proxy -- -l --config imports_granularity=Module,group_imports=StdExternalCrate,reorder_imports=true
```

These rust-analyzer settings for VSCode should help retain this style:
```json
  "rust-analyzer.imports.group.enable": true,
  "rust-analyzer.imports.prefix": "crate",
  "rust-analyzer.imports.merge.glob": false,
  "rust-analyzer.imports.granularity.group": "module",
  "rust-analyzer.imports.granularity.enforce": true,
```

proxy/src/auth/credentials.rs

@@ -1,20 +1,22 @@
 //! User credentials used in authentication.
 
-use crate::{
-    auth::password_hack::parse_endpoint_param,
-    context::RequestMonitoring,
-    error::{ReportableError, UserFacingError},
-    metrics::{Metrics, SniKind},
-    proxy::NeonOptions,
-    serverless::SERVERLESS_DRIVER_SNI,
-    EndpointId, RoleName,
-};
+use std::collections::HashSet;
+use std::net::IpAddr;
+use std::str::FromStr;
+
 use itertools::Itertools;
 use pq_proto::StartupMessageParams;
-use std::{collections::HashSet, net::IpAddr, str::FromStr};
 use thiserror::Error;
 use tracing::{info, warn};
 
+use crate::auth::password_hack::parse_endpoint_param;
+use crate::context::RequestMonitoring;
+use crate::error::{ReportableError, UserFacingError};
+use crate::metrics::{Metrics, SniKind};
+use crate::proxy::NeonOptions;
+use crate::serverless::SERVERLESS_DRIVER_SNI;
+use crate::{EndpointId, RoleName};
+
 #[derive(Debug, Error, PartialEq, Eq, Clone)]
 pub(crate) enum ComputeUserInfoParseError {
     #[error("Parameter '{0}' is missing in startup packet.")]
@@ -249,10 +251,11 @@ fn project_name_valid(name: &str) -> bool {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use serde_json::json;
     use ComputeUserInfoParseError::*;
 
+    use super::*;
+
     #[test]
     fn parse_bare_minimum() -> anyhow::Result<()> {
         // According to postgresql, only `user` should be required.