kvcache: optimize View() method and fix redundant atomic store

[VolodymyrBg]

The commit improves the View() method in the kvcache package by:

1. Removing redundant atomic store operation in OnNewBlock() after CompareAndSwap
2. Adding proper lock protection when accessing shared state in View()
3. Using time.NewTimer instead of time.After to prevent potential goroutine leaks
4. Optimizing ready state check flow to reduce lock contention

The changes make the code more efficient while maintaining thread safety.

[VolodymyrBg]

@AskAlexSharov Done