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.

Beginne mit dem im Issue verlinkten README-Setup-Abschnitt und reproduziere die lokale `.aio`-Konfiguration mit dem Cloud Manager IMS-Kontext. Prüfe das Upstream-Issue #67 von `aio-lib-ims`, um die globale Token-Persistenz zu verstehen, dokumentiere anschließend die Einschränkung und ermittle den erforderlichen Upstream-Fix; abgeschlossen ist die Aufgabe, wenn lokale Zugangsdaten nicht mehr global persistiert werden oder die Einschränkung klar dokumentiert ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.