macros 2.0

[vlada-shubina]

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Problem

Macros are pain point for a while when it comes to refactoring and code understanding. I struggled a lot to write documentation for them as interfaces were very vague.

Docs effort: fixes https://github.com/dotnet/templating/issues/5028 fixes https://github.com/dotnet/templating/issues/4616

Solution

This is 7.0.2xx(?)/8.0.1xx effort.

• created better interfaces for macro component based on generics
• created base types for macro and macro config implementation that do common actions
• cleaned up the logic of macro processing
  • if macro relies on other variable, and this variable doesn't exist - the processing stops
  • changed logic in GeneratePort macro - previously macro was not releasing socket until the macro is run. Now tracking the list of assigned ports instead.
• added logging
• fixed https://github.com/dotnet/templating/issues/5028

TODO:

• [x] add doc on how to add a new macro
• [x] localization
• [x] better unit tests

Checks:

• [x] Added unit tests
• [x] Added #nullable enable to all the modified files ?

[vlada-shubina]

@JanKrivanek I would like to kick of the review of this PR, though I'm still working on improving the test coverage.

The areas of review:

• new macro component interfaces - it would be good to have it pre-ready in case we start to support custom components.
• updated macro logic and improved parsing of the configuration with error handling.
• documentation

[vlada-shubina]

Open tasks:

• agree on coalesce behavior
• investigate bug when TemplateCreator can return null
• investigate how often float and hex types are used