Option to sort all map-like constructs for deterministic output (upstream #201)

[xe-nvdk]

Upstream: vmihailenco#201

Request for an encoder option to sort all map-like constructs (including struct members) deterministically. Enables reproducible serialization for hashing and digital signature use cases.

Note: SetSortMapKeys exists but only covers map[string]string, map[string]bool, and map[string]interface{}.