Add function to initialize set from elements

[joshua-kim]

Why this should be merged

Add a way for us to initialize a set with a pre-defined list of items. This avoids the one-liner we currently have to do of:

s := set.Set[ids.NodeID]{nodeID: struct{}{}}

and now we can just do:

s := set.Of[ids.NodeID](nodeID)

This PR adds this new function to the set package and replaces usages in avalanchego.

How this works

Calls Add for each element passed into Of

How this was tested

Added a UT

[danlaine]

Looks correct to me. Only questions are:

1. In this PR, should we use this in more places? i.e. in addition to occurrences where we do : struct{}{}
2. Should we name this SetOf in anticipation of adding functions ShortSetOf / NodeIDSetOf?

[joshua-kim]

In this PR, should we use this in more places? i.e. in addition to occurrences where we do : struct{}{}

Hm yeah we definitely can. I did a deeper scan and found some spots we can replace usages where we're also creating an empty set then calling Add on a predefined list of elements.

Should we name this SetOf in anticipation of adding functions ShortSetOf / NodeIDSetOf?

Hmm personally I dislike repeating package names as I think set.Of sounds better than set.SetOf. I think set[ids.ShortID].Of and set[ids.NodeID].Of should be enough for now? I'm not sure what making separate signatures for ids.ShortID and ids.NodeID would give us that aren't already provided by the generic type

[danlaine]

In this PR, should we use this in more places? i.e. in addition to occurrences where we do : struct{}{}

Hm yeah we definitely can. I did a deeper scan and found some spots we can replace usages where we're also creating an empty set then calling Add on a predefined list of elements.

Should we name this SetOf in anticipation of adding functions ShortSetOf / NodeIDSetOf?

Hmm personally I dislike repeating package names as I think set.Of sounds better than set.SetOf. I think set[ids.ShortID].Of and set[ids.NodeID].Of should be enough for now? I'm not sure what making separate signatures for ids.ShortID and ids.NodeID would give us that aren't already provided by the generic type

Ah totally forgot we no longer have the ShortSet and NodeIDSet types anymore lol nvm

[darioush]

nit: I wonder if we should call this FromList instead of Of?

[joshua-kim]

I went with Of because I'm used to Guava (java framework)'s ImmutableSet.of(1, 2, 3, 4, 5) syntax. If people feel like FromList or From or With (or other alternatives?) is better we can do that is well but they all seem pretty similar sounding to me 👍

[StephenButtolph]

Can we remove the unnecessary type annotations?

[StephenButtolph]

small nits