Debugger: Implement remaining part of #11033.

TeamDebugInfo:
- Add function to invalidate a source entry's file mapping.
UserInterfaceListener:
- Add listener hook to be able to invoke the aforementioned invalidate.
  Add corresponding implementation in TeamDebugger.
FileManager:
- When asked to locate a source entry, invalidate any existing mapping
  first.
TeamWindow:
- Always allow choosing an alternate source file.
- If we already have an existing source mapping, invalidate it first
  before attempting to establish a new one.

src/apps/debugger/controllers/TeamDebugger.h

@@ -66,6 +66,8 @@ private:
 	virtual void				SourceEntryLocateRequested(
 									const char* sourcePath,
 									const char* locatedPath);
+	virtual void				SourceEntryInvalidateRequested(
+									LocatableFile* sourceFile);
 	virtual	void				ImageDebugInfoRequested(Image* image);
 	virtual	void				ValueNodeValueRequested(CpuState* cpuState,
 									ValueNodeContainer* container,