`analysis_server_plugin`: async visitors

[RohitSaily]

environment:
  sdk: '3.10.0-162.1.beta' 
  # Dart SDK version: 3.10.0-162.1.beta (beta) (Mon Sep 1 23:24:50 2025 -0700) on "macos_x64"

dependencies:
  analysis_server_plugin: 0.2.2

when using a visitor that performs async operations, reports do not end up happening. eg with a SimpleASTVisitor<Future<void>>:

@override Future<void> visitMethodDeclaration(MethodDeclaration declaration) async
{  await Future.microtask(()=>rule.reportAtNode(declaration))
}

the report never happens

cc @srawlins