[python-sdk] Add a minimal type tag implementation
[python-sdk] Add a minimal type tag implementation

This currently is not robust as it doesn't support vectors or nexted
structs. Note: signers aren't used in any code that would be used for clients.

aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core