Rename the MCP connection manager to McpConnectionSet (#34708)

## What changed

- Use `McpConnectionSet` as the primary name for the collection of active MCP
  server connections throughout `codex-mcp` and its callers.
- Keep `McpConnectionManager` as a backward-compatible type alias.

GitOrigin-RevId: 9753838b4fd0a0b6429a9c4af0c077137616f388

codex-rs/core/src/connectors.rs

@@ -33,7 +33,7 @@ use codex_login::AuthManager;
 use codex_login::CodexAuth;
 use codex_mcp::CODEX_APPS_MCP_SERVER_NAME;
 use codex_mcp::MCP_TOOL_CODEX_APPS_META_KEY;
-use codex_mcp::McpConnectionManager;
+use codex_mcp::McpConnectionSet;
 use codex_mcp::McpRuntimeContext;
 use codex_mcp::ToolInfo;
 use codex_mcp::ToolPluginProvenance;
@@ -238,7 +238,7 @@ pub async fn list_accessible_connectors_from_mcp_tools_with_mcp_manager(
     let codex_apps_auth_manager =
         codex_mcp::host_owned_codex_apps_enabled(&mcp_config, auth.as_ref())
             .then(|| Arc::clone(&auth_manager));
-    let mcp_connection_manager = McpConnectionManager::new(
+    let mcp_connection_manager = McpConnectionSet::new(
         &mcp_servers,
         config.mcp_oauth_credentials_store_mode,
         config.auth_keyring_backend_kind(),