refactor(stdlibs): remove Hash, GetTimestamp, FormatTimestamp from std

[thehowl]

GetTimestamp and FormatTimestamp have been deprecated a while ago, and since the language is still changing and these are used nowhere in the source except for a test, it makes sense to remove them.

std.Hash comes from a discussion in #580. rg std.Hash returns nothing in the gno source, and in a bit of an obscure way, is not just a call to Sha256Sum, but a 20-byte version of that (see pkgs/gnolang/hash_image.go). I also removed some dead code in hash_image.go.

[moul]

It looks good to me, however, I’d like to ask @jaekwon if he sees good reasons to still keep this, because he was the original author.

[thehowl]

Merged master and pinging @jaekwon to review this

[jaekwon]

reading

[jaekwon]

I think this might be the right thing to do, but it's a bit weird.

One, we need to make sure that the declaration of type Location is safe, for when Location is ever set (now or in the future). So for example, Location shouldn't be modifiable, otherwise any user can modify a *Location for all users, a bad security breach. Not only should we scan the stdlibs/time code, but also I guess everything about the current implementation, including functions that haven't been ported yet, to make sure it will always be safe to completely port it and maintain it.

Also, it seems a bit unnecessary to support this time implementation because (a) it is a struct, which is more expensive than a primary value, (b) at least in the blockchain context we don't need to support that weird "wall timer" thing, (c) it honestly seems way too complex even in Go because of the "wall timer" thing. So I imagine we may want to implement another "time" package for gno in the future that is simpler.

But anyways, the stdlibs/time.Format is already used for boards, so seems fine to go ahead for now.

[thehowl]

@jaekwon Agreed in many ways, though I think maybe a good idea to port these thoughts to an issue tracking this.

My thoughts balooned into a large wall of text, so I've created #851 to track this.

I'll be merging this in the meantime.