Comparison methods panic for differently sized matrices

Wouldn't it make more sense to return `false`? It's not obvious to me that comparing dynamically-sized matrices of different size is necessarily a bug.

_Originally posted by @Ralith in https://github.com/dimforge/nalgebra/issues/1568#issuecomment-3478437643_

The methods in question that `assert!(self.shape() == other.shape())`:
```rs
Matrix::relative_eq()
Matrix::eq()
Matrix::abs_diff_eq()
Matrix::ulps_eq()
```