Extend QtC API for telemetry purposes

To provide more comprehensive telemetry information we'd like to have some additional APIs:

•  DebuggerKitInformation::debugger(kit) allows to get debugger version via DebuggerItem class. Good to have compiler version via ProjectExplorer::ToolChainKitInformation::toolChain(kit, ProjectExplorer::Constants::CXX_LANGUAGE_ID) as well.
• extend Welcome page API to allow track clicks on tutorial items as some of them guides to help documents, other to web, another to youtube, etc. It is possible to track opened tutorials as projects, as help documents, other types are non-traceable for now.
• provide access to QHelpEngine Class instance to catch signals from its content classes with help URL opened, keywords searches, content indexes opened, document titles, etc.