Missing multiple "Set-Cookie" key in Header 

## 🐶 Brief
Some users reported that if the header has many `Set-Cookie`, Proxyman only captures the last one. It happens in Request and Response too.

Technically, Proxyman store key-value of header as a Dictionary, so it overrides if it's same key. We should fix it.

## 👑 Criteria
- [ ] The header shouldn't be override 
- [ ] Retain the order of key when sending (current behavior)