CLIFTON, New Jersey — Along with aisles of diapers and colorful onesies, Target shoppers in some of the retailer's big-box stores can now find baby brands typically carried by specialty boutiques. Shoppers can see, feel and test strollers, car seats and high chairs outside of cardboard boxes at about 200 stores, or roughly 10% of the retailer's footprint. They can find merchandise from high-end brands, including a $1,000 UPPAbaby stroller. And customers can browse nearly 2,000 new baby items, which are available across all of the retailer's stores and online. Target's "baby boutiques," which have rolled out over the past two months, are just one piece of a broader push to refresh stores and woo a crucial customer base: busy families, who have increasingly turned to rivals like Walmart .…