Replace pop and pop_before with remove_current in Linked List Cusors

The name "pop" was critized in the discussion thread but despite agreement
it should be changed, no one did. This commit implements basically the
suggestion by Amanieu (but `remove_current` instead of `remove`). There is
some discussion however, over if there should be two methods (differing in
what element is the current one after deletion). This should be discussed
in the tracking issue before stabilizing the feature.

Author: LukasKalbertodt

text/2570-linked-list-cursors.md

@@ -71,7 +71,7 @@ fn remove_replace<T, P, F>(list: &mut LinkedList<T>, p: P, f: F)
             None => break,
         };
         if should_replace {
-            let old_element = cursor.pop().unwrap();
+            let old_element = cursor.remove_current().unwrap();
             cursor.insert_after(f(old_element));
         }
         cursor.move_next();
@@ -171,10 +171,9 @@ impl<'list T> CursorMut<'list, T> {
     /// Insert `item` before the cursor
     pub fn insert_before(&mut self, item: T);
 
-    /// Remove and return the item following the cursor
-    pub fn pop(&mut self) -> Option<T>;
-    /// Remove and return the item before the cursor
-    pub fn pop_before(&mut self) -> Option<T>;
+    /// Remove the current item. The new current item is the item following the
+    /// removed one.
+    pub fn remove_current(&mut self) -> Option<T>;
 
     /// Insert `list` between the current element and the next
     pub fn splice_after(&mut self, list: LinkedList<T>);