Switch runtime to cloud config bundle (#24622)

## Summary

- Adapts the moved `codex-cloud-config` crate from the legacy cloud
requirements endpoint to the new config bundle endpoint.
- Switches runtime consumers from `CloudRequirementsLoader` to
`CloudConfigBundleLoader` so one shared bundle supplies cloud-delivered
config and requirements.
- Removes the legacy cloud requirements domain loader path.

## Details

This intentionally keeps `codex-cloud-config` monolithic for review
lineage: the previous PR establishes the crate move, and this PR shows
the behavior change against that moved implementation. A follow-up PR
splits the module back into focused files.

The new bundle path preserves the important cloud requirements loader
semantics where intended: account-scoped signed cache, 30 minute TTL, 5
minute refresh cadence, retry/backoff, auth recovery, and fail-closed
startup loading. The cached payload changes from a single requirements
TOML string to the backend-delivered bundle, and validation rejects
malformed config or requirements fragments before cache write/use.

codex-rs/core-plugins/src/test_support.rs

@@ -3,7 +3,6 @@ use std::path::Path;
 
 use crate::OPENAI_CURATED_MARKETPLACE_NAME;
 use crate::PluginsConfigInput;
-use codex_config::CloudRequirementsLoader;
 use codex_config::LoaderOverrides;
 use codex_config::NoopThreadConfigLoader;
 use codex_config::loader::load_config_layers_state;
@@ -106,7 +105,6 @@ pub(crate) async fn load_plugins_config(codex_home: &Path, cwd: &Path) -> Plugin
         Some(cwd),
         &[],
         LoaderOverrides::without_managed_config_for_tests(),
-        CloudRequirementsLoader::default(),
         &NoopThreadConfigLoader,
     )
     .await