Create TTL map with time wheel architecture and tests

* Implement TTLMap with DashMap + time wheel for O(1) TTL operations
* Add 10 test cases covering basic functionality, manual GC, and concurrent access
* Add concurrent tests with multiple async tasks for safety verification
* The TTL map uses a circular time wheel for efficient batch expiration,
avoiding the performance issues of retain() operations on large maps
* Tests validate O(1) TTL operations, proper expiration batching, and thread
safety of the DashMap + time wheel architecture

Author: jayshrivastava

src/common/mod.rs

@@ -1 +1,2 @@
+pub mod ttl_map;
 pub mod util;