Unified syntax

[andrei-marinica]

Description of the pull request (what is new / what has changed)

Documentation of:

• the unified transaction syntax
• the new blackbox tests
• migration from the old calls to the new syntax
• migration of the old blackbox tests to the new

Also somewhat reorganized the Rust test section.

Did you test the changes locally ?

• [x] yes
• [ ] no

Which category (categories) does this pull request belong to?

• [x] document new feature
• [x] update documentation that is not relevant anymore
• [x] add examples or more information about a component
• [ ] fix grammar issues
• [ ] other