[analysis_server] Allow the ApplyCodeAction command to be called via LSP-over-Legacy

This updates the `ApplyCodeActionCommandHandler` to be a "shared" command that can work for either kind of server (although it does not yet allow calling over DTD - the executeCommand handler still requires trusted callers).

It also moves all of the tests into a shared mixin so they will be run for both server kinds.

Change-Id: I831cc5a1a9feadc528e5b33b82e3469c60111dfa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/427440
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

https://dart.googlesource.com/sdk/+/036b5996fb03bfd33aebcbbec2c9081b3d8a067a
diff --git a/DEPS b/DEPS
index 9f9eef4..9486aae 100644
--- a/DEPS
+++ b/DEPS
@@ -234,7 +234,7 @@
 ]
 
 deps = {
-  'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '050b74063051b4b2f5edbcf372e62414affadaae',
+  'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '036b5996fb03bfd33aebcbbec2c9081b3d8a067a',
 
   'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '83082c19b72717dbc6504cf38ce920b402440e04',
 
diff --git a/commits.json b/commits.json
index 7c3807a..b20ec82 100644
--- a/commits.json
+++ b/commits.json
@@ -1,4 +1,4 @@
 {
   "flutter":"83082c19b72717dbc6504cf38ce920b402440e04",
-  "flutter/engine/src/flutter/third_party/dart":"050b74063051b4b2f5edbcf372e62414affadaae"
+  "flutter/engine/src/flutter/third_party/dart":"036b5996fb03bfd33aebcbbec2c9081b3d8a067a"
 }
\ No newline at end of file