Add new cases for troubleshooting guide

[yizha1]

During negative testing, several issues were reported on Notation CLI, see follows:

• Misleading error message when trust store is not configured notation#699
• Misleading error message if no permission to read certificates from trust store notation#700
• Misleading error message when no certificates were stored in the trust store notation#701

After discussion in the community, these issues couldn't be fixed in Notation v1 release, but it is worth adding these issues to troubleshooting guide. The mitigation is the same for all three issues, that is, user can run the command with --verbose or -v flag to see details of the error, and which helps users to understand what is happening and what to do next.