Introduce DisplayRow, MultiBufferRow newtypes and BufferRow type alias (#11656)

Part of https://github.com/zed-industries/zed/issues/8081

To avoid confusion and bugs when converting between various row `u32`'s,
use different types for each.
Further PRs should split `Point` into buffer and multi buffer variants
and make the code more readable.

Release Notes:

- N/A

---------

Co-authored-by: Piotr <piotr@zed.dev>

crates/editor/src/selections_collection.rs

@@ -14,7 +14,8 @@ use util::post_inc;
 use crate::{
     display_map::{DisplayMap, DisplaySnapshot, ToDisplayPoint},
     movement::TextLayoutDetails,
-    Anchor, DisplayPoint, ExcerptId, MultiBuffer, MultiBufferSnapshot, SelectMode, ToOffset,
+    Anchor, DisplayPoint, DisplayRow, ExcerptId, MultiBuffer, MultiBufferSnapshot, SelectMode,
+    ToOffset,
 };
 
 #[derive(Debug, Clone)]
@@ -308,7 +309,7 @@ impl SelectionsCollection {
     pub fn build_columnar_selection(
         &mut self,
         display_map: &DisplaySnapshot,
-        row: u32,
+        row: DisplayRow,
         positions: &Range<Pixels>,
         reversed: bool,
         text_layout_details: &TextLayoutDetails,