go: support TreeMap

[wenchy]

References

• https://github.com/emirpasic/gods/tree/master/trees/redblacktree ✔️
• https://github.com/elliotchance/orderedmap
• https://github.com/umpc/go-sortedmap

Implement treemap pkg in pathpkg/treemap

Define a new generic type Pair

To encapsule orderedmap and struct as a pair (as up-level orderedmap's value).

type Pair[T any, U any] struct {
    First T
    Second U
}

Generated APIs for ActivityConf

• GetOrderedMap()
• GetOrderedMap1(activityId uint64) (XXX, error)
• GetOrderedMap2(activityId uint64, chapterId uint32) (XXX, error)
• GetOrderedMap3(activityId uint64, chapterId uint32, sectionId uint32) (XXX, error)