chore: replace usage of new() with default()

[Ethan-000]

Related issue(s)

Related to #874

Description

See Constructors section of the guide in the issue

Summary of changes

1. Add impl Default to new() functions that do not take inputs.
2. Change new() to call the default function. (update: remove empty new())
   // 3. vec![] to Vec::new() (discarded this change)

// I'm not sure if removing new() functions is a good idea (this seems to be what the guide is suggesting from my //understanding) so I changed them to calling the default function.

Dependency additions / changes

Test additions / changes

Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.
• This PR requires documentation updates when merged.

Additional context

[jfecher]

I'm unsure of this refactoring - I don't think it improves readability by much and don't think we should strictly follow a style guide even for small items.

In regards to having both T::new and T::default, my preference would be to only having T::default (if it can be automatically derived, or it is required for a T: Default bound), or T::new otherwise. No need to have 2 functions that do the same thing.

[guipublic]

If new does not do anything special, I am OK to replace it with default, it enables other types to automatically derive if they use one with default. I also agree that in that case we can keep only default and not have both.

[Ethan-000]

didn't mean to remove review request @guipublic @kevaundray