[analyzer/linter] Simplify implementation of rule State

There hasn't been a need to make a separate custom State, so get rid of the label field and instead rely on a sealed hierarchy.

Change-Id: I31319049f210b0c9fbd0be9cf89925b2c9da49fa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/399360
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>

https://dart.googlesource.com/sdk/+/e70a91d8e381af00d76d3c0a89a859c4bbd4bef9

DEPS

diff --git a/DEPS b/DEPS
index 4cee224..df64ad7 100644
--- a/DEPS
+++ b/DEPS
@@ -258,7 +258,7 @@
 
   'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + 'ee35d0bdcf6944e4e3421081e2a79e63b0dd3a9e',
 
-  'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'ee5c4b00840aa254b30b04eaaea186e7c0345f61',
+  'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'e70a91d8e381af00d76d3c0a89a859c4bbd4bef9',
 
   'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '047cbb01f48d1aa30965bbd2373cafb86d26f7d4',
 

commits.json

diff --git a/commits.json b/commits.json
index 16bc51e..92d3e22 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "engine/src/flutter":"ee35d0bdcf6944e4e3421081e2a79e63b0dd3a9e",
-  "engine/src/flutter/third_party/dart":"ee5c4b00840aa254b30b04eaaea186e7c0345f61",
+  "engine/src/flutter/third_party/dart":"e70a91d8e381af00d76d3c0a89a859c4bbd4bef9",
   "flutter":"047cbb01f48d1aa30965bbd2373cafb86d26f7d4"
 }
\ No newline at end of file