A cancelled GDB startup whose process stop could not be confirmed retained a
capability error. The next cleanup retry then reported "This analysis is
unavailable for the current target" instead of the caller's cancellation.
Move Rizin's retention rule (the #5963 fix) into one shared
retainedDebuggerCleanupFailure in src/process/ownedDebuggerSession.ts and use
it from both session managers. The GDB command-cancel path now retains the
cancellation itself, so retry reports no longer depend on Set insertion order.