Roll dart_style 3.0.1 into the SDK.

This is a minor change with just bug fixes:

* Handle trailing commas in for-loop updaters (#1354).
* Format `||` patterns like fallthrough cases in switch expressions (#1602).
* Handle comments and metadata before variables more gracefully (#1604).
* Ensure comment formatting is idempotent (#1606).
* Better indentation of leading comments on property accesses in binary operator
  operands (#1611).
* Don't crash on doc comments in local variable declarations (#1621).

This won't affect much code, but it does change the formatting in some cases.

Change-Id: I2d52fee92aecbc24315e4f1a89360af85ec85942
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401482
Auto-Submit: Bob Nystrom <[email protected]>
Commit-Queue: Alexander Thomas <[email protected]>
Reviewed-by: Alexander Thomas <[email protected]>

Author: munificent

DEPS

@@ -130,7 +130,7 @@ vars = {
   #   and land the review.
   #
   # For more details, see https://github.com/dart-lang/sdk/issues/30164.
-  "dart_style_rev": "1de89eb3bd340315f9ff5f2afc319cc1d6131b8d", # disable tools/rev_sdk_deps.dart
+  "dart_style_rev": "21de99ec0ff8ace4d946a746fb427fffd6afa535", # disable tools/rev_sdk_deps.dart
   "dartdoc_rev": "c7f11603effa88ddacabfd555993f322fca8b3fe",
   "ecosystem_rev": "b4b2a438ff40cbbdf245b2854567316c1d24a394",
   "flute_rev": "e4ea0459a7debae5e9592c85141707b01fac86c9",