Bump tools to 3440b74e430051304b56d4acd71b7ed30ab1855d

Changes:
```
> git log --format="%C(auto) %h %s" b98c535..3440b74
 https://dart.googlesource.com/tools.git/+/3440b74 Prep mime 2.0.0 for publish (594)
 https://dart.googlesource.com/tools.git/+/03cedfb coverage: update test mocks (592)
 https://dart.googlesource.com/tools.git/+/57aa604 unified_analytics: fix new lint (593)

...

 https://dart.googlesource.com/tools.git/+/2c6801a Formatters take IOSink rather than using global env for output
 https://dart.googlesource.com/tools.git/+/6b18fc0 Add version, author, homepage, dependency version constraints to pubspec
 https://dart.googlesource.com/tools.git/+/52ea0df Initial import

```

Diff: https://dart.googlesource.com/tools.git/+/b98c535537101eff0484ba279bd4090a5b9ac2ad..3440b74e430051304b56d4acd71b7ed30ab1855d/
Change-Id: I3630a3d5dbf1fded03711e7cb6ce2d25dbccc737
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/387600
Reviewed-by: Nate Bosch <nbosch@google.com>
Commit-Queue: Devon Carew <devoncarew@google.com>

DEPS

@@ -184,7 +184,7 @@ vars = {
   "test_descriptor_rev": "3b85d384997bd8cc0454475045cbb4ffc68797ee",
   "test_process_rev": "6223572ca16d7585d5f08d9281de6a5734e45150",
   "test_reflective_loader_rev": "6e648863b39aab8d0204e769d25805eea9db0ac4",
-  "tools_rev": "b98c535537101eff0484ba279bd4090a5b9ac2ad",
+  "tools_rev": "953e254ca1efc45c461aa04cb2703782d35d7830",
   "typed_data_rev": "2bb9e6ead6394e2d4ec6068c5ece8b2ec0e2b945",
   "vector_math_rev": "2cfbe2c115a57b368ccbc3c89ebd38a06764d3d1",
   "watcher_rev": "0484625589d8512b36a7ad898a6cc6351d24c556",