[Reliability] Add failsafe decoding when String is received for stock_quantity#9850

rachelmcr merged 3 commits intotrunkwoocommerce/woocommerce-ios:trunkfrom

issue/9840-nsdecimal-decoding-fallbackswoocommerce/woocommerce-ios:issue/9840-nsdecimal-decoding-fallbacksCopy head branch name to clipboard