WASHINGTON — Some polar bears and their cubs already in danger of extinction could be legally killed by private oil-drilling projects in northern Alaska, according to proposed new regulations.  The planned regs — part of of President Trump’s oil lease program and awaiting approval by the US Fish and Wildlife Service — would allow for the “incidental, unintentional take” of a small number of the majestic white bears, as well as Pacific walruses, by energy companies in a critical habitat without