## Problem
proxy params being a `HashMap<String,String>` when it contains just
```
application_name: psql
database: neondb
user: neondb_owner
```
is quite wasteful allocation wise.
## Summary of changes
Keep the params in the wire protocol form, eg:
```
application_name\0psql\0database\0neondb\0user\0neondb_owner\0
```
Using a linear search for the map is fast enough at small sizes, which
is the normal case.
9a081c230f