GHSA-2326-pfpj-vx3h: lexical-core has multiple soundness issues

RUSTSEC-2024-0377 contains multiple soundness issues:

1. Bytes::read() allows creating instances of types with invalid bit patterns
2. BytesIter::read() advances iterators out of bounds
3. The BytesIter trait has safety invariants but is public and not marked unsafe
4. write_float() calls MaybeUninit::assume_init() on uninitialized data, which is is not allowed by the Rust abstract machine
5. radix() calls MaybeUninit::assume_init() on uninitialized data, which is is not allowed by the Rust abstract machine

Version 1.0 fixes these issues, removes the vast majority of unsafe code, and also fixes some correctness issues.