THE chief drama of Jakarta is its contrasts, a fascinating collision of East and West. Great rivers of steel, glass and cinder blocks wind through endless expanses of helter-skelter one- and two-story neighborhoods with far too few parks to alleviate the landscape. But few visitors to the “Big Durian” realize that they are able to relax and keep fit even in a city as teeming, hectic and traffic-tangled as Jakarta. Start by checking ou