[ Widget Preview ] Crash when .dart_tool/widget_preview_scaffold/.dart_tool doesn't exist on subsequent runs #178660
Description
This can happen if flutter widget-preview start is interrupted or flutter pub get isn't run in the widget_preview_scaffold project when it's first initialized.
Example Logs
StateError: Bad state: Could not determine run package name. Project path "/private/var/folders/_y/rdj_3wtj5mbbtf6syy_2cw6800d8lv/T/flutter_widget_preview_test.HHIWrz/.dart_tool/widget_preview_scaffold/" did not occur as package root in package config "/private/var/folders/_y/rdj_3wtj5mbbtf6syy_2cw6800d8lv/T/flutter_widget_preview_test.HHIWrz/.dart_tool/package_config.json". Please report a reproduction on https://github.com/flutter/flutter/issues/169475.
```console
#0 DartBuild.build (package:flutter_tools/src/build_system/targets/native_assets.dart:50:7)
<asynchronous suspension>
#1 _BuildInstance._invokeInternal (package:flutter_tools/src/build_system/build_system.dart:915:9)
<asynchronous suspension>
#2 FlutterBuildSystem.build (package:flutter_tools/src/build_system/build_system.dart:662:16)
<asynchronous suspension>
#3 FlutterHookRunnerNative.runHooks (package:flutter_tools/src/build_system/targets/hook_runner_native.dart:30:35)
<asynchronous suspension>
#4 ResidentWebRunner._updateDevFS (package:flutter_tools/src/isolated/resident_web_runner.dart:760:28)
<asynchronous suspension>
#5 ResidentWebRunner.run.<anonymous closure> (package:flutter_tools/src/isolated/resident_web_runner.dart:324:41)
<asynchronous suspension>
#6 asyncGuard.<anonymous closure> (package:flutter_tools/src/base/async_guard.dart:108:24)
<asynchronous suspension>