Fix wslservice lifetime callback teardown to stop long-run threadpool resource buildup

[Copilot]

Summary of the Pull Request

On long-running WSL1 workloads, wslservice.exe can accumulate large commit size and thread count. This change tightens LifetimeManager teardown so per-client threadpool waits/timers are explicitly canceled/unregistered when callbacks are removed or globally cleared.

PR Checklist

• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

• Scoped fix: LifetimeManager::ClearCallbacks

  • Cancels callback timers before releasing ownership.
  • Unregisters threadpool waits (SetThreadpoolWait(..., nullptr, nullptr)) before releasing ownership.
  • Moves released wait/timer handles into local WIL RAII containers so teardown completes outside the lock.

• Scoped fix: LifetimeManager::RemoveCallback

  • Applies the same explicit timer cancellation and wait unregistration for single-callback removal.
  • Drains released threadpool objects outside the lock to avoid lock-held teardown and reduce residual callback resources.

• Behavioral intent

  • Prevent stale callback-associated threadpool resources from persisting across long service lifetimes.

if (oldClient.timer)
{
    SetThreadpoolTimer(oldClient.timer.get(), nullptr, 0, 0);
    timers.emplace_back(oldClient.timer.release());
}

for (auto& process : oldClient.clientProcesses)
{
    SetThreadpoolWait(process.terminationWait.get(), nullptr, nullptr);
    waits.emplace_back(process.terminationWait.release());
}

Validation Steps Performed

• Focused static/code-path validation of LifetimeManager callback removal and global clear flows.
• No user-facing/API contract changes; no localization or documentation deltas introduced.

[Copilot]

Pull request overview

This PR tightens LifetimeManager teardown in wslservice.exe to prevent long-running WSL1 scenarios from accumulating threadpool wait/timer resources by explicitly canceling/unregistering per-client threadpool objects and draining them outside m_lock.

Changes:

• Update LifetimeManager::ClearCallbacks() to cancel timers and unregister waits, then re-home threadpool handles into draining WIL RAII containers outside the lock.
• Update LifetimeManager::RemoveCallback() to apply the same cancel/unregister + drain behavior for single-client removal.
• Add OwnedProcess::CancelWait() helper to centralize unregistering a threadpool wait.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/windows/service/exe/Lifetime.h	Adds OwnedProcess::CancelWait() declaration to support explicit wait unregistration during teardown.
src/windows/service/exe/Lifetime.cpp	Implements cancel/unregister + out-of-lock draining for waits/timers in ClearCallbacks and RemoveCallback, and defines OwnedProcess::CancelWait().

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.