AccessToken is always stored in global config below the IMS context

When using a local `.aio` config file similar to what is outlined in https://github.com/adobe/aio-cli-plugin-cloudmanager?tab=readme-ov-file#setup-for-oauth-integration with `aio config:set ims.contexts.aio-cli-plugin-cloudmanager PATH_TO_CONFIG_JSON_FILE --file --json --local` I expect that the accessToken which is retrieved is also stored locally, however this is persisted in the global aio config due to https://github.com/adobe/aio-lib-ims/issues/67 like this.

```
ims: {
contexts: {
aio-cli-plugin-cloudmanager: {
...
// duplicated service credentials from the local .aoi file
...
access_token: {
token: ",
expiry: ...
}
},
```

In order to be able to easily switch between different credentials/organization just using the local AIO config (https://github.com/adobe/aio-lib-core-config/tree/master?tab=readme-ov-file#project-configuration) is not enough. Instead one currently has to use dedicated/unique IMS context names and always pass that via `imsContextName` to each `aio cloudmanager` command as workaround.

Please document that limitation in the readme and try to fix the upstream bug in https://github.com/adobe/aio-lib-ims/issues/67.

Issue でリンクされている README のセットアップセクションから始め、Cloud Manager IMS コンテキストを使用してローカルの `.aio` 設定を再現します。グローバルなトークン永続化の仕組みを理解するために、`aio-lib-ims` の upstream issue #67 を確認し、その後で制限事項を文書化して、必要な upstream fix を特定します。ローカル認証情報がグローバルに永続化されなくなるか、制限事項が明確に文書化されれば完了です。

索引モデルが issue の本文から書いたものです。