[AWS CloudWatch] `cloud.account.name` shows wrong value for cross-account metrics (uses CloudWatch label instead of IAM alias)

When collecting CloudWatch metrics from a linked AWS account using role_arn, cloud.account.name is populated with the CloudWatch cross-account observability label (typically the AWS Organizations account name) instead of the IAM account alias.

Root cause: At startup, the code correctly resolves the IAM alias via `ListAccountAliases` and stores it in `MonitoringAccountName`. However, `createEvents()` in `cloudwatch.go` ignores this value and uses the raw `${PROP('AccountLabel')}` from the CloudWatch `GetMetricData` response, which resolves to the AWS Organizations account name, not the IAM alias.

Start in cloudwatch.go, especially createEvents(), and trace how MonitoringAccountName is populated by ListAccountAliases during startup. Compare that value with the raw AccountLabel from the GetMetricData response for role_arn cross-account collection. Done means cloud.account.name uses the IAM alias rather than the CloudWatch observability label.

Written by the indexing model from the issue text.