Implement upstream generating of data model in case schema was updated

[rkharisov]

Currently we need to track if schema was updated and manually download schema and regenerated models. It will be very convenient if it can be done automatically. How I see this

Possible flow:

• merge in iroha2 repository to branch iroha2-dev branch triggers action in iroha2-java repository
• action downloads schema.json artifact and compare hash of the downloaded artifact with previous one
• if the hash is the same that means schema was not changed and nothing need to do
• if it is different then action replace existing schema in repository and create pull request.
• action updates schema version. This is final step for this action
• in PR another action generates schema and run tests

[Mingela]

Possible only for minor releases which is not usually case

[arndey]

Possible only for minor releases which is not usually case
agree