style: updated rustfmt.toml guidelines

[alejandro-vaz]

this PR introduces the following changes to rustfmt.toml:

1. changes import granularity to one, which means that all imports are grouped under a single use block
2. cargo fmt --check errors on overflow and unformatted
3. set one blank line as the maximum
4. set float literals to only have trailing zeros if they don't have postfix
5. allowed small functions to be written in a single line of code
6. set import layout to vertical
7. automatically convert /* ... */ comments to // ... comments
8. allowed rustfmt to reorder implementations
9. prohibited rustfmt to inline simple structs (it hurts readability)
10. set style edition to 2024
11. told rustfmt not to introduce trailing commas
12. suggested rustfmt to prefer ? try shortcut
13. allowed rustfmt to inline simple where clauses

effects

• we can no longer use the vec! macro because rustfmt confounds the macro with the module, reducing the imports alloc::vec; alloc::vec::Vec to alloc::vec::{self, Vec} which is not valid
• at line 2108, not being able to use the vec! macro means that we use iterator-collection specialization instead
• saves 80 lines of code

[jdm]

Personally I am not a fan of this style of writing imports, since they are harder to search for (eg when looking if a dependency is unused) and I find them harder to read. I will defer to you since you're actually working in the code, however.

[jdm]

I'm not convinced about the value of smashing methods into one line like this because it makes the visual syntactic noise much higher.

[alejandro-vaz]

I will revert that one then