ISTANBUL — Fluttering down from the skies over the Gaza Strip on a recent day were clouds of flyers dropped by the Israeli military asking for tips on the whereabouts of top Hamas leaders. “The end of Hamas is near,” the flyers proclaimed in Arabic, promising hefty bounties to anyone who helped bring about the arrest of those who had “brought destruction and ruin to the Gaza Strip.” The Hamas leader in Gaza, Yehia Sinwar, headed the list in exchange for a reward of $400,000 — more than 1,500 tim