In warehouse spec.interval, support cron style times

[tal-hason]

Checklist

• I've searched the issue queue to verify this is not a duplicate feature request.

Proposed Feature

In warehouse spec.interval, support "cron" style times so it will be simpler to set an interval for a specific day in a week or any other config

Motivation

if I have multi-stage release pipelines, and I release to the GA channel once a week, so I want that specific warehouse will only check for new commits once a week.

using a "cron" style interval will be more flexible.