feat(frontend): support async function for captured context and impl pg_is_in_recovery(), rw_recovery_status()

[yezizp2012]

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What's changed and what's your intention?

Resolve #17522 . This PR supports async function for capture_context and impl rw_recovery_status() and real pg_is_in_recovery() based on the status from meta node. The following is the code generated for rw_recovery_status:

fn rw_recovery_status_impl(
    meta_client: &Arc<dyn FrontendMetaClient>,
) -> impl std::future::Future<Output = Result<RecoveryStatus>> + Send + 'static {
    let meta_client = meta_client.clone();
    async move {
        {
            meta_client
                .get_cluster_recovery_status()
                .await
                .map_err(|e| ExprError::Internal(e.into()))
        }
    }
}
async fn rw_recovery_status_impl_captured() -> Result<RecoveryStatus> {
    { META_CLIENT::try_with(|meta_client| rw_recovery_status_impl(meta_client)) }?.await
}

The return value is one of the following ones: STARTING, RECOVERING and RUNNING.

Checklist

• I have written necessary rustdoc comments
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Release note

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Support function rw_recovery_status, pg_is_in_recovery.

[fuyufjh]

The rest LGTM

[BugenZhao]

Add support for a PG-compatible function indicating the status of RW cluster is good, but I'm wondering whether it's better to provide a customized function like rw_recovery_status returning more detailed information (like distinguishing "starting" and "failure recovery") for internal usages such as Cloud.

Rest LGTM

[wangrunji0408]

LGTM