Backport: Standardize JSON formatting of action data

[linh2931]

Those two should go together.

EOSIO/eos#10100

old code doing this:
act.data ------can parse to json object ? if yes "data"=json object and hex_data = "hex string"
if no "data" = "hex string"

new code doing this:
act.data ------can parse to json object ? if yes "data"=json object and hex_data = "hex string"
if no "hex_data" = "hex string"

and extract function also some changes correspondingly.

Also, please see related test PR here:

EOSIO/eos#10405

[heifner]

This change needs to be done at a major release point and clearly communicated. It affects all clients as it changes the JSON format.

[linh2931]

Not saving to data field is a breaking backward compatibility change. It is agreed not do it. #659 is created to track the hex_field change