Codecs - part 4

[andreibancioiu]

This is part of a series of pull requests.

See: https://github.com/multiversx/mx-sdk-py/pull/32.

This can be reviewed side-by-side with:

• https://github.com/multiversx/mx-sdk-abi-go/blob/main/abi/parts.go
• https://github.com/multiversx/mx-sdk-abi-go/blob/main/abi/shared.go
• https://github.com/multiversx/mx-sdk-abi-go/blob/main/abi/multiValues.go
• https://github.com/multiversx/mx-sdk-abi-go/blob/main/abi/constants.go