refactor: replace `Default` for clarity

[hamirmahal]

This pull request replaces Default::default() with T::default() where T is the type of the default value, to make it more clear which default we are using.

I followed the checklist:

• [ ] I added unittests
• [x] I ran make check without errors
• [ ] I tested the overall application
• [ ] I added an appropriate item to the changelog

[hamirmahal]

@extrawurst are you open to this change?