Add templating processor for native apps

[sfc-gh-melnacouzi]

Pre-review checklist

• I've confirmed that instructions included in README.md are still correct after my changes in the codebase.
• I've added or updated automated unit tests to verify correctness of my new code.
• I've added or updated integration tests to verify correctness of my new code.
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• I've described my changes in the release notes.
• I've described my changes in the section below.

Changes description

SNOW-1508576:
Added templating support for arbitrary files.
To do this, user has to add templates processor to their artifacts:

native_app:
  name: myapp
  artifacts:
    - src: app/*
      dest: ./
      processors:
        - templates

[sfc-gh-bdufour]

a little bikeshedding necessary for 'templating' here. How do we refer to the templates feature in public docs again?

[sfc-gh-melnacouzi]

documentation is being updated to refer to these as template or templates:
Project definition file templates instead of Project definition file templating.

I think we can switch to templates for this. WDYT?

[sfc-gh-melnacouzi]

or template expansion as another option

[sfc-gh-bdufour]

+1 for templates then

[sfc-gh-melnacouzi]

updated

[sfc-gh-pjafari]

trivial but can you update templating to templates in the pr description as well :')

[sfc-gh-bdufour]

why does it inherit from temp dir? Seems like unnecessary coupling at first glance. I'm not even sure why this needs to be a context manager. Can you explain the thought process?

[sfc-gh-melnacouzi]

This worked nicely in the tests, but I think I can try to separate tmp directory part from the setup part.

[sfc-gh-melnacouzi]

refactored.