Fix warnings and compile errors on nightly (#6886)

Nightly has added a bunch of compiler and linter warnings. There is also
two dependencies that fail compilation on latest nightly due to using
the old `stdsimd` feature name. This PR fixes them.

compute_tools/src/compute.rs

@@ -18,8 +18,6 @@ use futures::future::join_all;
 use futures::stream::FuturesUnordered;
 use futures::StreamExt;
 use postgres::{Client, NoTls};
-use tokio;
-use tokio_postgres;
 use tracing::{debug, error, info, instrument, warn};
 use utils::id::{TenantId, TimelineId};
 use utils::lsn::Lsn;

compute_tools/src/extension_server.rs

@@ -71,7 +71,7 @@ More specifically, here is an example ext_index.json
     }
 }
 */
-use anyhow::{self, Result};
+use anyhow::Result;
 use anyhow::{bail, Context};
 use bytes::Bytes;
 use compute_api::spec::RemoteExtSpec;

compute_tools/src/http/api.rs

@@ -13,8 +13,6 @@ use compute_api::responses::{ComputeStatus, ComputeStatusResponse, GenericAPIErr
 use anyhow::Result;
 use hyper::service::{make_service_fn, service_fn};
 use hyper::{Body, Method, Request, Response, Server, StatusCode};
-use num_cpus;
-use serde_json;
 use tokio::task;
 use tracing::{error, info, warn};
 use tracing_utils::http::OtelName;