feat(compute_ctl): use TLS if configured (#10972)

Closes: https://github.com/neondatabase/cloud/issues/22998

If control-plane reports that TLS should be used, load the certificates
(and watch for updates), make sure postgres use them, and detects
updates.

Procedure:
1. Load certificates
2. Reconfigure postgres/pgbouncer
3. Loop on a timer until certificates have loaded
4. Go to 1

Notes:
1. We only run this procedure if requested on startup by control plane.
2. We needed to compile pgbouncer with openssl enabled
3. Postgres doesn't allow tls keys to be globally accessible - must be
read only to the postgres user. I couldn't convince the autoscaling team
to let me put this logic into the VM settings, so instead compute_ctl
will copy the keys to be read-only by postgres.
4. To mitigate a race condition, we also verify that the key matches the
cert.

Cargo.toml

@@ -112,7 +112,7 @@ hyper0 = { package = "hyper", version = "0.14" }
 hyper = "1.4"
 hyper-util = "0.1"
 tokio-tungstenite = "0.21.0"
-indexmap = "2"
+indexmap = { version = "2", features = ["serde"] }
 indoc = "2"
 ipnet = "2.10.0"
 itertools = "0.10"