aws:download content document to support tokenInfo from cross account ssm parameter

I would like to run command from multiple accounts within the organization. Instead of creating a github token parameter in each account, I would like to only create one in the management account and share it across the organization.

Right now, `secure-string-token` in `"tokenInfo":"{{ssm-secure:secure-string-token}}"` is the name of parameter within the same account, I would like it to should support arn as well so that we can get the parameter as a shared resource from another account.

No file or test is named in the issue. Start by tracing how tokenInfo and the ssm-secure parameter reference are parsed and retrieved, then verify the AWS cross-account parameter path; done means a shared parameter ARN can supply the token across accounts while the existing same-account name still works.

Written by the indexing model from the issue text.