Refactor ipQueue to use generics

[neilalexander]

This refactors ipQueue to use Go generics. Since there are now considerably less interface boundaries, there should be far less small runtime allocations and less potential for nils to creep out by accident and cause panics during type assertions.

Signed-off-by: Neil Twigg neil@nats.io

[derekcollison]

LGTM

[ripienaar]

Are there any comparative benchmarks? Might be a non issue but generics do have some perf concerns

[neilalexander]

Are there any comparative benchmarks? Might be a non issue but generics do have some perf concerns

I have ran a number of benchmarks on this branch vs main, this branch reduces allocations slightly but there's no change in throughput.

[gedw99]

Nice work @neilalexander