Rename Abort terminator to Terminate

Unify terminology used in unwind action and terminator, and reflect
the fact that a nounwind panic is triggered instead of an immediate
abort is triggered for this terminator.

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -218,7 +218,7 @@ pub trait Machine<'mir, 'tcx>: Sized {
         unwind: mir::UnwindAction,
     ) -> InterpResult<'tcx>;
 
-    /// Called to evaluate `Abort` MIR terminator.
+    /// Called to abort evaluation.
     fn abort(_ecx: &mut InterpCx<'mir, 'tcx, Self>, _msg: String) -> InterpResult<'tcx, !> {
         throw_unsup_format!("aborting execution is not supported")
     }

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -144,7 +144,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 }
             }
 
-            Abort => {
+            Terminate => {
                 M::abort(self, "the program aborted execution".to_owned())?;
             }