Which are the leading shadow IT discovery tools available today, and how do they compare in terms of capabilities such as automatic detection of unmanaged or unauthorized applications, integration with existing IT and security systems, depth of visibility across cloud and on-premises environments, risk scoring and prioritization, reporting and analytics dashboards, ease of deployment and use, scalability for small to enterprise-level organizations, support for real-time monitoring, API and customization options, and overall effectiveness in reducing security blind spots and improving IT governance?