Udaan, the fastest Indian startup to achieve unicorn status, has raised $585 million in its latest round of funding, valuing the online business-to-business marketplace at $2.5-3 billion. The Series D round saw investments from Tencent, Altimeter Capital, Footpath Ventures, Hillhouse, GGV Capital and Citi Ventures, the firm said on Wednesday. Existing investors Lightspeed Venture Partners and DST Global also invested…