[NU-1466] ScenarioAction: commands (ADT, sum types) instead of methods

[arkadius]

Describe your changes

DeploymentManager's "action" methods - (methods operating on a scenario or its deployment) were replaced by case classes and one method handling them all: processCommand(command):

• validate - ValidateScenarioCommand
• deploy - RunDeploymentCommand
• cancel with deploymentId argument - CancelDeploymentCommand
• cancel without deploymentId argument - CancelScenarioCommand
• stop with deploymentId argument - StopDeploymentCommand
• stop without deploymentId argument - StopScenarioCommand
• savepoint - MakeAScenarioSavepointCommand
• test - TestScenarioCommand

Checklist before merge

• [ ] Related issue ID is placed at the beginning of PR title in [brackets] (can be GH issue or Nu Jira issue)
• [ ] Code is cleaned from temporary changes and commented out lines
• [ ] Parts of the code that are not easy to understand are documented in the code
• [ ] Changes are covered by automated tests
• [ ] Showcase in dev-application.conf added to demonstrate the feature
• [ ] Documentation added or updated
• [ ] Added entry in Changelog.md describing the change from the perspective of a public distribution user
• [ ] Added MigrationGuide.md entry in the appropriate subcategory if introducing a breaking change
• [ ] Verify that PR will be squashed during merge