Make rewrapping take tabs more into account (#20196)

Closes #18686


https://github.com/user-attachments/assets/e87b4508-3570-4395-92b4-c5e0e9e19623


Release Notes:

- The Rewrap command now considers the width of each tab character at
the beginning of the line to be the configured tab size.

---------

Co-authored-by: Will <will@zed.dev>

crates/language/src/buffer.rs

@@ -46,6 +46,7 @@ use std::{
     future::Future,
     iter::{self, Iterator, Peekable},
     mem,
+    num::NonZeroU32,
     ops::{Deref, DerefMut, Range},
     path::{Path, PathBuf},
     str,
@@ -4325,6 +4326,13 @@ impl IndentSize {
         }
         self
     }
+
+    pub fn len_with_expanded_tabs(&self, tab_size: NonZeroU32) -> usize {
+        match self.kind {
+            IndentKind::Space => self.len as usize,
+            IndentKind::Tab => self.len as usize * tab_size.get() as usize,
+        }
+    }
 }
 
 #[cfg(any(test, feature = "test-support"))]