Release hot-reload input resources and retired callbacks

[bartasc4]

After a hot reload, an idle executor thread and retained inactive hook handles/callback parameters can outlive their useful work. Refused or failed requests can also leave received DEX resources unconsumed. This change releases those framework-owned resources while allowing in-flight callbacks to finish on the generation they entered.

• Use a serial worker that exits when its queue drains and releases the queue storage. Preserve FIFO dispatch and recover from task, reporter and thread-start failures.
• Consume DEX inputs in order and release every received handle/mapping on success, refusal and failure. Report cleanup failures without losing whether the generation already changed.
• Release inactive handles' callback records, avoid retaining an old generation through reload parameters, and skip empty callback-snapshot allocations. Preserve hook identities, atomic replacement and in-flight snapshots.

Applies directly to master. This is resource-lifetime cleanup; it does not change the reload negotiation policy or replace #992. It is independent of daemon reconnection #1017 and #1012; the three changes were also built/tested together.

Validation and limits

Validation: clean-source Kotlin and four-ABI native builds; host tests exercise production classes and native callback operations, including 3,000 replacements, 8,000 concurrent queue submissions, 100 drained batches, and DEX failure cleanup. On Android 12 with NeoZygisk, a local validation build completed two consecutive reloads in one application process, then two more after a KernelSU emulated soft reboot. Retained old callback parameters did not prevent retired module/loader weak references from clearing; in-flight callbacks completed, the idle reload worker exited, and the process FD count stayed flat. The clean PR sources were built separately from that local validation build.

Limits: host SharedMemory tests use controlled doubles. The change releases framework-owned references and DEX inputs; ART controls reclamation of its own DEX memory. It does not unload native module libraries or reclaim objects deliberately retained by module/application code.