Go 1.22 upgrade check list

[roman-khimov]

• for loops ranging over integers/constants are too good to be unused, searching for := 0 finds a lot of them
• replace math/rand with math/rand/v2, changes there are not significant for us, but still we better be up to date
• cmp.Or can be considered, but I'm not sure we have any cases for it
• AppendDecode and AppendEncode can be useful for base64/hex manipulations
• slices.Concat can be considered

See https://go.dev/doc/go1.22 also.

[roman-khimov]

append(bytes.Clone()...) is a nice pattern to search for wrt slices.Concat.