Fix vim code working on display map chars (#10103)

Release Notes:

- vim: Fixed motion bugs when softwrap, folds or inlay hints were used.

crates/multi_buffer/src/anchor.rs

@@ -137,3 +137,6 @@ impl AnchorRangeExt for Range<Anchor> {
         self.start.to_point(content)..self.end.to_point(content)
     }
 }
+
+#[derive(Clone, Copy, Eq, PartialEq, Debug, Hash, Ord, PartialOrd)]
+pub struct Offset(pub usize);

crates/multi_buffer/src/multi_buffer.rs

@@ -1,6 +1,6 @@
 mod anchor;
 
-pub use anchor::{Anchor, AnchorRangeExt};
+pub use anchor::{Anchor, AnchorRangeExt, Offset};
 use anyhow::{anyhow, Result};
 use clock::ReplicaId;
 use collections::{BTreeMap, Bound, HashMap, HashSet};