Small improvements of the Scenario Management API

[FabienLelaquais]

Description

I have a few recommendations to make on the Core API.

• the taipy.create_global_data_node() and taipy.create_scenario() functions both expect a Config object (DataNode/Scenario) to operate.
  I would be far more comfortable with a method create() on the two Config classes.
  Shorter, object oriented, less error-prone.
  And just like Scenario.set_primary() that I love.

• the argument 'name' to create_scenario() is confusing.
  A 'name' does not hold semantics except identification... which is not the purpose.
  This should be called 'label', for what it does: provide a human-readable string that a log file can show, or how scenarios should appear in the user interface.

• taipy.configure_scenario() should also have a 'label' argument for the exact same purpose.
  The scenario_selector control let you create new scenarios from a configuration. Unfortunately, all the control can display is the identifier for those ScenarioConfigs. These must be identifiers, therefore not customizable for a proper human reader.

Acceptance Criteria

• Ensure new code is unit tested, and check code coverage is at least 90%.
• Create related issue in taipy-doc for documentation and Release Notes.
• Check if a new demo could be provided based on this, or if legacy demos could be benefit from it.
• Ensure any change is well documented.

Code of Conduct

• I have checked the existing issues.
• I am willing to work on this issue (optional)