DAS plugins: Fix "interesting files" glob

In testing, I saw that _added_ files were not being analyzed at all by
plugins. It turned out that `PluginManager.broadcastWatchEvent` uses
that glob to decide if watch events should be broadcast to a given
plugin isolate. It uses this Glob to determine that answer:

```dart
Glob(
  _resourceProvider.pathContext.separator,
  pattern,
).matches(filePath)
```

and using `'*.dart'` for that pattern, always answers "no, this file
does not match '*.dart'"; I believe `**.dart` is the correct glob
pattern we should use.

Change-Id: Id99d758151629c485884ba20e4d1f49f574f5889
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/452160
Commit-Queue: Samuel Rawlins <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: srawlins

pkg/analysis_server_plugin/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.3.2-dev
+
+- Fix support for automatic re-analysis of '*.dart' files _added_, both on-disk
+  and for files added in the IDE.
+
 ## 0.3.1
 
 - Write more of a README.

pkg/analysis_server_plugin/lib/src/plugin_server.dart

@@ -252,7 +252,7 @@ class PluginServer {
     // the SDK path is configured...
     _sdkPath = parameters.sdkPath;
     return protocol.PluginVersionCheckResult(true, 'Plugin Server', '0.0.1', [
-      '*.dart',
+      '**.dart',
     ]);
   }
 

pkg/analysis_server_plugin/pubspec.yaml

@@ -1,6 +1,6 @@
 name: analysis_server_plugin
 description: A framework and support code for building plugins for the analysis server.
-version: 0.3.1
+version: 0.3.2-dev
 repository: https://github.com/dart-lang/sdk/tree/main/pkg/analysis_server_plugin
 
 environment: