(Bloomberg) -- Rivian Automotive Inc. lost its claim to be Tesla Inc.’s most credible competitor long ago. Now, its ability to navigate an EV demand slowdown poses its biggest test.Most Read from BloombergLargest Covid Vaccine Study Yet Finds Links to Health ConditionsCapital One to Buy Discover for $35 Billion in Year's Biggest Deal Amazon Deserves to Be Called Out for Swindling UsersA $6 Trillion Wall of Cash Is Holding Firm as Fed Delays CutsYour 401(k) Will Be Gone Within a DecadeWith even a