Migrate to Rust 1.95.0 / Edition 2024

[petamoriken]

The changes are as follows:

• Remove extern crate declarations
• Add crate:: prefix to internal module paths
• Rename macro_rules! try to try_from (reserved keyword in Edition 2018+)
• Replace static lookup tables and test data with const
• Wrap unsafe operations in explicit unsafe {} blocks (unsafe_op_in_unsafe_fn)
• Add build.rs to register #[cfg(cargo_c)]
• Add dep: prefix to optional dependencies in [features]
• Update .rustfmt.toml (removed deprecated options)

Accidentally, the code updates and formatting were combined into a single commit. I apologize for making it difficult to read.

[petamoriken]

I ran cargo fmt while overlooking the following part of rustfmt.toml:

# Note that this rustfmt file only provides rough
# guidelines about how the style should be.
# Right now, rustfmt is not capable to map all
# demands to the code style (yet).

What approach should I take to fix this?