executor: update kcov remote coverage interface
executor: update kcov remote coverage interface

The kcov extension is being upstreamed and the interfaces has been changed.

google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller