Invalidate anchors when they get deleted (#14116)

Allows deleting the outputs directly within the editor. This also fixes
the overlap logic to make sure that the ends and the starts are
compared.


https://github.com/zed-industries/zed/assets/836375/84f5f582-95f3-4c6a-a3c9-54da6009e34d

Release Notes:

- N/A

---------

Co-authored-by: Antonio <antonio@zed.dev>

crates/repl/Cargo.toml

@@ -24,6 +24,7 @@ futures.workspace = true
 image.workspace = true
 language.workspace = true
 log.workspace = true
+multi_buffer.workspace = true
 project.workspace = true
 runtimelib.workspace = true
 schemars.workspace = true