.Net: [Feature Branch] Improvements and tests for declarative processes

[dmytrostruk]

Motivation and Context

This PR contains a couple of improvements and tests for declarative processes:

1. Added parsing of workflow wrapper on top of non-wrapper declarative format.
2. Added a possibility to specify ID for declarative steps.
3. Fixed the registration of dotnet node by using node ID instead of agent ID.
4. Added unit tests to verify process import from YAML which contains both dotnet and declarative nodes and is compatible with VS Code extension.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄