Debugger: Further work on memory leak hunting.
TeamWindow:
- Properly delete stack frame selection entries in destructor.
TeamDebugger:
- The reference to TeamDebugInfo wasn't correctly initialized to own,
leading to TeamDebugInfo never being destroyed.
FunctionInstance:
- Also clear source code reference in destructor.
ImageDebugInfo:
- Release references to specific infos in destructor. These are acquired
on our behalf when loading the image info, but were never released,
leading to the latter never being freed.
DwarfManager:
- Release references to files in destructor.
FileManager:
- Release entries in various destructors.
Somewhat improves the situation in #13800, but is still far from complete,
as a thorough review of this nature hasn't ever really been done.