feat: Official Iterator support for Go1.23+ & minor fixes

[leonardodalinky]

I made official supports of iter package in Go standard for #33. Now we can try the range-based for-loops to iterate some of the types!

I use //go:build go1.23 build tag for these files with new features to avoid breaking changes, like the code written in previous Go version (<1.23). I think this will not do harm to the users using older Go compilers.

All the types with naive Iterators are implemented with new Iter(), Iter2(), IterMut() and IterMut2():

• array
• deque
• bidlist
• simplelist
• treemap: exclude IterMut()
• rbtree: exclude IterMut()
• set: only Iter()
• slice
• vector

Example for array:

a := array.New[int](10)

// Iter()
for v := range a.Iter() {
    fmt.Println(v)
}

// IterMut()
for vPtr := range a.IterMut() {
    *vPtr *= 2
}

// Iter2()
for i, v := range a.Iter2() {
    fmt.Println(i, v)
}

// IterMut2()
for i, vPtr := range a.IterMut2() {
    *vPtr = i
}