Code actions use lots of text edits for small changes

Example reproducer:

1. Clone https://github.com/kak-lsp/kak-lsp (I'm using 1ffcd26021fb2f5818353254e9e15042852bbedb)
2. Open src/main.rs in your editor
3. Goto line 46, the one with use std::path::Path;
4. Hover over std::path::Path and run the code action "Merge Imports".

To apply "Merge Imports", rust-analyzer sends a sequence of 274 text edits, some extending to unrelated lines like 315.
This feels a bit weird because their sum is just this:

diff --git a/src/main.rs b/src/main.rs
index 11b623c..53ac623 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -45,4 +45,3 @@ use std::os::unix::net::UnixStream;
 use std::panic;
-use std::path::Path;
-use std::process::{Command, Stdio};
+use std::{path::Path, process::{Command, Stdio}};
 

perhaps we can make this more minimal?

Of course this difference is not user-visible in most clients.
However, the LSP client kak-lsp leaks this noise to the user in some scenarios:
it applies each text edit directly inside the Kakoune editor (kind of as if the user had made the edit).
Now when the user undoes the code action, Kakoune will use a heuristic to select the ranges that were touched by the text edits. In this case it selects much more than just the two affected lines, which is unfortunate.

I guess various clients have their own ways of squashing sequences of text edits.
Undo works properly in VSCode, but it's probably based on a diff of the old/new buffer contents.
Computing this diff seems unnecessary if we already have the text edits; we should just make them simpler.

(FWIW kak-lsp currently has a bug on the reproducer: it modifies unrelated lines, probably because it doesn't interpret text edits correctly)

rust-analyzer version: rust-analyzer 2022-01-17

rustc version: rustc 1.56.1 (59eed8a2a 2021-11-01

Reproduce the "Merge Imports" action in kak-lsp using src/main.rs and the pinned rust-analyzer version described in the issue. Start by tracing how this action produces its sequence of text edits; done means the same import merge is represented by minimal edits limited to the affected lines, without changing unrelated ranges.