Default dataset in integration packages is formed as <package name>.<data stream name>, both in elastic-package and Fleet.

In the case of input packages, elastic-package is forming it as something <package name>.<policy template name>, but Fleet uses only the policy template name.

This can be seen for example in https://github.com/elastic/integrations/pull/15785/files#diff-aedcaf1181208657e4674a02592b841c2adfcc3fecef0dae25c32b452e39cf14R10.

Adjust the behavior in elastic-package so it uses the same defaults as Fleet.