What problem does this solve or what need does it fill?

Using the latest edition enables the new features and improvements from the compiler.

What alternative(s) have you considered?

Keep the 2021 edition for the moment.

Additional context

The migration seems very straightforward with just some warning with unsafe code in the tests.
I am interested in taking care of the upgrade if it's ok for you.
I'd just like to know whether I should use the oldest compatible version of Rust (1.85) or the most recent (1.87) ?