Add AtomicCountingBloomFilter

[MovAh13h]

A lock-free counting bloom filter that supports concurrent insertion and deletion — combining the semantics of CountingBloomFilter with the thread-safety of AtomicBloomFilter.

• Lock-free insert(&self) via ConcurrentFilter using a CAS loop for saturating u8 counter increments (no fetch_add to avoid wrapping)
• Lock-free remove(&self) -> bool with a two-pass check+CAS-decrement approach that prevents underflow under concurrent removes
• clear(&mut self) for exclusive reset
• Manual Debug and Clone (Acquire loading per element)
• Serde support via shadow Data struct (same pattern as AtomicBloomFilter)
• Full test suite: construction errors, no false negatives (proptest), deletion, concurrency (8 threads × 1 000 items), statistical FPR bounds

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