ch-remote: add env_logger, log messages to stderr

Until now all messages generated using `log::level!`
(e.g., `warn!`) have not been printed as `ch-remote` did not
register a logger.
Furthermore, replace all `eprintln!` with `error!`
to align formatting for consistency.

Signed-off-by: Maximilian Güntner <code@mguentner.de>

Cargo.toml

@@ -33,6 +33,7 @@ anyhow = "1.0.94"
 api_client = { path = "api_client" }
 clap = { version = "4.5.13", features = ["string"] }
 dhat = { version = "0.3.3", optional = true }
+env_logger = { workspace = true }
 epoll = "4.3.3"
 event_monitor = { path = "event_monitor" }
 hypervisor = { path = "hypervisor" }