[lldb] remove somewhat dangerous 'd'(etach) and 'k'(ill) shortcuts

'd' would be much better used for up/down shortcuts, and this also removes
the possibility of ruining the whole debugging session by accidentally
hitting 'd' or 'k'. Also change menu to have both 'detach and resume'
and 'detach suspended' to make it clear which one is which. See
discussion at https://reviews.llvm.org/D68541 .

Differential Revision: https://reviews.llvm.org/D68908