chore: add String() method to IDSlice type

[EclesioMeloJunior]

Description

• Initialize and preallocate the slice of strings
• use the method String for each ID and put in the slice
• return a string of ids separated by ,

Tiny demonstration: https://go.dev/play/p/kd_nd-edWnr

Original suggestion -> ChainSafe/gossamer#2267 (comment)

[marten-seemann]

Why is this needed? The linked issue doesn't seem to have a lot to do with it. The link is about a race condition, certainly a stringer function can't help with that.

[EclesioMeloJunior]

@marten-seemann sorry for the abrupt PR 😅 . I propose these changes, not because of the race condition but from a comment that came up there and I thought that would be ok if IDSlice have a String() method to help with logs, let me know if this is not required

[qdm12]

I proposed to add a String() method forgetting it was from this repository. @EclesioMeloJunior created the PR to add this.

This can be quite nice so we can use i.e. fmt.Sprintf("%s", peer.IDSlice{}) and it would print nicely.