feat: replace custom LRU cache with otter cache library

[rhymf14]

Replace internal LRU cache implementation for prepared statements and routing key info with the more efficient otter cache library.

🤖 Generated with Claude Code

[worryg0d]

Hi @rhymf14.

I had a quick look to understand the changes better, and here’s a short breakdown:

1. I see that it replaces gocql’s built-in LRU cache with the external caching library maypok86/otter. The motivation behind this change isn’t entirely clear—could you share the main goal? Adding some benchmarks to compare both implementations would also be good.
2. There’s no GitHub issue or Jira ticket linked. Having one would be great for tracking purposes.
3. This patch bumps the required Go version to 1.24.6, which is a big jump from the current 1.19 used on the trunk branch.
4. It looks like the patch doesn’t include recent changes from trunk, such as CASSGO-1 and CASSGO-22. Since they overlap with this implementation, it may be worth reconciling them.