Allow unwrap() in tests when clippy::unwrap_used is denied (#11616)

## Problem

The proxy denies using `unwrap()`s in regular code, but we want to use
it in test code
and so have to allow it for each test block.

## Summary of changes

Set `allow-unwrap-in-tests = true` in clippy.toml and remove all
exceptions.

proxy/src/serverless/conn_pool.rs

@@ -189,7 +189,6 @@ impl ClientDataRemote {
 }
 
 #[cfg(test)]
-#[expect(clippy::unwrap_used)]
 mod tests {
     use std::sync::atomic::AtomicBool;
 

proxy/src/serverless/json.rs

@@ -256,7 +256,6 @@ fn pg_array_parse_inner(
 }
 
 #[cfg(test)]
-#[expect(clippy::unwrap_used)]
 mod tests {
     use serde_json::json;
 

proxy/src/serverless/local_conn_pool.rs

@@ -367,7 +367,6 @@ fn sign_jwt(sk: &SigningKey, payload: &[u8]) -> String {
 }
 
 #[cfg(test)]
-#[expect(clippy::unwrap_used)]
 mod tests {
     use ed25519_dalek::SigningKey;
     use typed_json::json;

proxy/src/serverless/sql_over_http.rs

@@ -1209,7 +1209,6 @@ impl Discard<'_> {
 }
 
 #[cfg(test)]
-#[expect(clippy::unwrap_used)]
 mod tests {
     use super::*;
 

proxy/src/serverless/websocket.rs

@@ -177,7 +177,6 @@ pub(crate) async fn serve_websocket(
 }
 
 #[cfg(test)]
-#[expect(clippy::unwrap_used)]
 mod tests {
     use std::pin::pin;