Infallible Vec operations

Some operations on a Vec<T, N> are infallible but can only be implemented using fallible methods. What do you think about adding more infallible methods? For example:

• from_array(data: [T; N]): construct a Vec from an array with the same capacity (would also be useful for constants)
• fill(&mut self, value: T): resize to capacity and clone value to empty slots
• fill_default(&mut self): resize to capacity and write T::default() to empty slots
• replace(&mut self, other: &Self): clear this Vec and copy the data from other

Review the existing fallible Vec<T, N> methods and the four proposed operations: from_array, fill, fill_default, and replace. Compare their intended behavior with the no-std, static-friendly constraints, then determine the API and tests needed for each method; done means the infallible operations are implemented with agreed semantics.