optimize entry cleanup

[SF-Zhou]

This PR optimizes the entry cleanup mechanism in LockMap by introducing a StateFlags struct that packs both the reference count and a "has value" flag into a single AtomicU32. This allows the cleanup logic to check both conditions atomically without needing to inspect the actual value under lock.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b018dc3) to head (c05ac23).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #25   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          871       901   +30     
=========================================
+ Hits           871       901   +30     

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[Copilot]

Pull request overview

This PR optimizes the entry cleanup mechanism in LockMap by introducing a StateFlags struct that packs both the reference count and a "has value" flag into a single AtomicU32. This allows the cleanup logic to check both conditions atomically without needing to inspect the actual value under lock.

Key changes:

• Introduced StateFlags struct with bit-packed reference count (31 bits) and has-value flag (1 bit)
• Replaced State<V>.refcnt with State<V>.flags throughout the codebase
• Updated entry drop implementations to set the value flag before attempting cleanup

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[Copilot]

Pull request overview

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

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