DedupAddrs should not allocate

[MarcoPolo]

Sort.Slice will allocate unfortunately :(
golang/go#17332

func BenchmarkDedupAddrs(b *testing.B) {
	b.ReportAllocs()
	tcpAddr := ma.StringCast("/ip4/127.0.0.1/tcp/1234")
	quicAddr := ma.StringCast("/ip4/127.0.0.1/udp/1234/quic-v1")
	wsAddr := ma.StringCast("/ip4/127.0.0.1/tcp/1234/ws")
	addrs := []ma.Multiaddr{tcpAddr, quicAddr, tcpAddr, quicAddr, wsAddr}
	for i := 0; i < b.N; i++ {
		addrs = DedupAddrs(addrs)
	}
}

Originally posted by @sukunrt in #2322 (comment)

[sukunrt]

I just wanted to fix the comment.
fix here: #2350
The allocations are low(3/op) so it's fine to leave it as is. Converting it to an O(n^2) in place algorithm might lead to performance issues. It is an overkill implementing a custom no allocation O(nlgn) algorithm for this.

[marten-seemann]

Are you sure there’s a performance penalty for a O(N^2) for small N? I’d expect it to be negligible for typical values of N.

[sukunrt]

I think you're right.

These are the benchmarks for an O(N^2) implementation:

BenchmarkDedupAddrs10-8          4220767               276.8 ns/op             0 B/op          0 allocs/op
BenchmarkDedupAddrs20-8          1315252               915.9 ns/op             0 B/op          0 allocs/op
BenchmarkDedupAddrs50-8           182114              6581 ns/op               0 B/op          0 allocs/op
BenchmarkDedupAddrs100-8           46258             25906 ns/op               0 B/op          0 allocs/op

Even if a node has 100 addrs(my kubo node has 15 before deduping), this isn't prohibitively expensive.

These are the numbers for the current implementation:

BenchmarkDedupAddrs10-8          6057549               192.2 ns/op            88 B/op          3 allocs/op
BenchmarkDedupAddrs20-8          3525658               338.6 ns/op            88 B/op          3 allocs/op
BenchmarkDedupAddrs50-8          1787802               670.7 ns/op            88 B/op          3 allocs/op
BenchmarkDedupAddrs100-8          974338              1204 ns/op              88 B/op          3 allocs/op

[marten-seemann]

There's https://pkg.go.dev/golang.org/x/exp/slices, which provides allocation-free sorting. I created #2395 to make use of that package.