Fix inconsistent use between jinja-templating and nsis code

[lrandersson]

Checklist

• [x] I added a descriptive title
• [x] I searched open requests and couldn't find a duplicate

What is the idea?

In another issue it was discussed that the NSIS templates contains a lot of inconsistencies between jinja-templating and NSIS code. Since NSIS and Jinja are used together, it would improve the code in terms of quality and readability if it was clearly defined in the codebase when we prefer to use Jinja vs NSIS logic. For example Jinja is preferred over NSIS when we work with for-loops, but there is also a lot of overlap between their functionality (if-statements for example).

We should clearly define how and when we want one or the other and update the code as necessary.

Why is this needed?

Developers would mainly benefit from this feature because it would make it easier to work with the NSIS templates.

What should happen?

1. Document when/where/how we want to use Jinja in the NSIS templates.
2. Update the code-base based on the documentation, or, if out of scope, create follow-up tickets.

Additional Context

No response