[BUG] messages/external folder imported twice due to missing glob exclusion

[xiata]

What happened?

In cli/plasmo/src/features/background-service-worker/bgsw-messaging.ts#getHandlerList there is a glob that inadvertently includes external messages when given getHandlerList(manifest, "messages"). The glob should not enter the messages/external folder because messages should only include internal message listeners, not the external message listeners.

How to reproduce:

1. Create an external message handler, e.g. src/background/external/messages/Test.ts
2. Create a .babelrc with at least the preset-env:

{
    "presets": [
      [
        "@babel/preset-env",
        {
          "targets": "chrome >= 90",
          "useBuiltIns": "usage",
          "corejs": 3
        }
      ],
      [
        "@babel/preset-typescript",
        {
          "allowDeclareFields": true
        }
      ]
    ]
  }

3. plasmo build. Note that the build will fail according to the external message handler you added.

Version

Latest

What OS are you seeing the problem on?

MacOSX

What browsers are you seeing the problem on?

Chrome

Relevant log output

🟣 Plasmo v0.89.2
🔴 The Browser Extension Framework
🔵 INFO   | Prepare to bundle the extension...
🔵 INFO   | Building for target: chrome-mv3
🔵 INFO   | Loaded environment variables from: [ '.env.chrome', '.env.production', '.env' ]
🔴 ERROR  | Identifier 'messagesExternalTest' has already been declared. (38:20)

### (OPTIONAL) Contribution

- [X] I would like to fix this BUG via a PR

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct
- [X] I checked the [current issues](https://github.com/PlasmoHQ/plasmo/issues?q=is%3Aopen+is%3Aissue+label%3Abug) for duplicate problems.

[xiata]

#1096