Switch to 2024 edition

[simo5]

The migration tool automatically changed some of thcode causing some churn. I manually changed some of the things, like removing expr_2021 from macros as it was not necessary and changing the renaming of the now reserved word gen from r#gen to generator.

A bunch of let Some() {} else () expressions were changed to matches, I let that be, sometime smatch turns out to be idiomatic, sometimes it is about the same readability.

Checklist

• Test suite updated with functionality tests
• Test suite updated with negative tests
• Documentation was updated
• This is not a code change

Reviewer's checklist:

• Any issues marked for closing are fully addressed
• There is a test suite reasonably covering new functionality or modifications
• This feature/change has adequate documentation added
• A changelog entry is added if the change is significant
• Code conform to coding style that today cannot yet be enforced via the check style test
• Commits have short titles and sensible text

[Jakuje]

lgmt. I find the matches most of the time easier to read than the if let Ok() ... constructs, but at some when there is a lot of code inside, they end up too indented ...

[Jakuje]

Should the edition be changed also in Cargo.toml ?

https://github.com/latchset/kryoptic/blob/main/Cargo.toml#L4

[simo5]

Should the edition be changed also in Cargo.toml ?

https://github.com/latchset/kryoptic/blob/main/Cargo.toml#L4

Well, I am confused, the migration is really about changing it in Cargo.toml which is how I started it ... I am really surprised the MR did not end up having it there, without the Cargo.toml change no change really happened. I will open a followup change to actually do the change then.

[simo5]

Filed #187