Add tags and metadata to the state machine states

[oEscal]

This is a simple subfeature of the feature implemented in #30.
It simply adds more information to each state machine state:

• Now, each state has tags with information regarding its workflow entity (if it is a function, a branch, a state, or even the type of state).
  • With these tags, the created graphs have distinct colors related to whether that state is associated with a function, a branch, a state, etc.
• Each state also has metadata with raw information regarding its workflow entity. For example, now a machine state related to a function will have that specific function definition.

Other minor fixes grouped in this PR:

• Foreach-related state machine states now have a transaction to themselves.
• The StateMachineGenerator class now receives the workflow once (and not its states one by one) and generates the state machine with only one call.

[cdavernas]

LGTM! Cheers ❤️