Support hostnames in iggy-bench

[hubcio]

Verify that iggy-bench accepts hostnames like localhost:8090 instead of just IP addresses. If it doesn't work, fix the validation or DNS resolution.

What to focus on:

• Test current behavior first — the issue might not exist
• Check SDK client configs for overly strict address validation
• If broken, fix DNS resolution rather than hardcoding IP-only validation

Done when iggy-bench pp tcp --server-address localhost:8090 works and a test confirms it.

Open questions:

• Does the issue actually exist?
• Is the problem in bench argument parsing or SDK client connection logic?

Nice to have: instead of server addr + port, make iggy-bench accept connection string, just like iggy CLI.

[seokjin0414]

@hubcio can i take this?