streamer: fix hardcoded unstaked connections throttling rate

[diman-io]

Problem

If I run a QUIC server with non-default settings like 2000/500, throttling unstaked connections by a constant 20% seems unfair.

agave/streamer/src/nonblocking/stream_throttle.rs

Line 14 in d221ad4

const MAX_UNSTAKED_STREAMS_PERCENT: u64 = 20;

Proposed Solution

Replace this in StakedStreamLoadEMA implementation with max_unstaked_connections / (max_staked_connections + max_unstaked_connections)