A social media post by London Mayor Sadiq Khan calling his city and Singapore global powerhouses has ignited scrutiny of both places, with critics arguing that they are worlds apart.Khan, who was in Singapore this week, posted a picture of himself standing in front of the Marina Bay skyline on Sunday with the caption: “This is what it looks like when two global powerhouses unite. Delighted to be here to bang the drum for London and supercharge the strong ties between our countries.”Social...