Debugger: Another set of #13800 fixes.

AbstractTable/Table/TreeTable:
- Let BColumnListView take care of deleting columns. The previous
approach was resulting in the columns being leaked.

Debugger:
- Don't detach the UI reference, as TeamDebugger will acquire its own.

GraphicalUserInterface:
- Cleanup of file panel handler.

SourceView:
- Clean up marker manager.

*Roster:
- Clean up registered objects in destructors.

GlobalTypeLookup:
- Clean up hash tables.

NetworkTargetHostInterfaceInfo:
- Fix reference handling for settings.

libdebugger: Fix missing init in TargetHostInterfaceRoster.

- When adding the TargetHostInterfaceInfos to the roster, Init() was not
called on the individual instances, leading to them potentially being
incomplete.

libdebugger: Add initial version of network interface.

NetworkTargetHostInterface{Info}:
- Barebones classes for implementing a target host interface over TCP.

Debugger: Split into core library and application.

- Add subfolder src/kits/debugger which contains the debugger's core
functionality and lower layers. Correspondingly add headers/private/debugger
for shared headers to be used by clients such as the Debugger application
and eventual remote_debug_server. Adjust various files to account for
differences as a result of the split and moves.
- Add libdebugger.so to minimal Jamfile.