Fix/protocol diff complexity

[pranavkonde]

Description

Fixes #3328

Optimizes the protocol diff implementation in identify/id.go from O(n²) to O(n) by using a map-based approach instead of nested loops.

Changes

// Before: O(n²)
for _, x := range b {
    for _, y := range a {
        if x == y {
            found = true

// After: O(n)
seen := make(map[protocol.ID]struct{}, len(a))
for _, x := range a {
    seen[x] = struct{}{}
}

[sukunrt]

Thanks @pranavkonde. Can you make this PR over master and not your other PR?

[sukunrt]

Can you do sort -> unique -> diff?
That'll make it not alloc for the map.