chore: put crypto provider logic in a shared crate (#11294)

Ensures a process-wide rustls crypto provider is installed.

Both the `codex-network-proxy` and `codex-api` crates need this.

codex-rs/utils/rustls-provider/src/lib.rs

@@ -0,0 +1,12 @@
+use std::sync::Once;
+
+/// Ensures a process-wide rustls crypto provider is installed.
+///
+/// rustls cannot auto-select a provider when both `ring` and `aws-lc-rs`
+/// features are enabled in the dependency graph.
+pub fn ensure_rustls_crypto_provider() {
+    static RUSTLS_PROVIDER_INIT: Once = Once::new();
+    RUSTLS_PROVIDER_INIT.call_once(|| {
+        let _ = rustls::crypto::ring::default_provider().install_default();
+    });
+}