`cloud.account.name` is not provided in Asset Inventory when using Asset Discovery integration with Cloud Connector feature

[maxcold]

Kibana version:
9.1-BC1

Elasticsearch version:
9.1-BC1

Describe the bug:
cloud.account.name is not being populated for Cloud Asset Discovery documents when no account alis has been configured.

While on CSPM cloudbeat we resolve the account name with this formula account name || account alias name (here and here), it seems that in asset discovery we only use account alias name (for example in iam role fetcher here )

Steps to reproduce:

1. deploy 9.1-BC on QA env in the available AWS region
2. enable beta integrations and navigate to Cloud Asset Discovery integration, select AWS single account or organization account, but make sure to use an account that has not alias configured
3. check ingested data

Expected behavior:
cloud.account.name should be present and containing the account name, in the documents

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

[elasticmachine]

Pinging @elastic/kibana-cloud-security-posture (Team:Cloud Security)