Collect user warnings from logs and store them

[sergsalatsky]

• CLOUDBLD-4643

Since we've added explicit user warnings in our logs, we have to collect and present them to the outputs, namely logs and task result.

Signed-off-by: Serhii Salatskyi ssalatsk@redhat.com

Maintainers will complete the following section

• [x] Commit messages are descriptive enough
• [x] Code coverage from testing does not decrease and new code is covered
• [x] JSON/YAML configuration changes are updated in the relevant schema
• [x] Pull request has a link to an osbs-docs PR for user documentation updates

[sergsalatsky]

This PR is blocked until osbs-client PR is merged

[MartinBasti]

koji-c CLI will be another PR?

[sergsalatsky]

koji-c CLI will be another PR?

Yes

[sergsalatsky]

Release note: User warnings are stored in the separate log file 'user_warnings.log'