Remove deprecated annotations and Refactor From implementations

[sinder38]

Motivation

I saw multiple instances of:

#[allow(deprecated)] // Can be changed when MSRV >= 1.53

Since the current MSRV is 1.66, these can be simplified.

tower-http/README.md

Line 40 in 35740de

tower-http's MSRV is 1.66.

This is not strictly a refactor, I replaced some specific array implementations with a blanket implementation.

Solution

Replaced array-based From implementations with a generic, iterable-based approach

// Before:
impl<const N: usize> From<[HeaderName; N]> for AllowHeaders {
    fn from(arr: [HeaderName; N]) -> Self {
        #[allow(deprecated)] // Can be changed when MSRV >= 1.53
        Self::list(array::IntoIter::new(arr))
    }
}

// After:
impl<I> From<I> for AllowHeaders
where
    I: IntoIterator<Item = HeaderName>,
{
    fn from(iter: I) -> Self {
        Self::list(iter)
    }
}

For Inner structs supporting conversions from a single item, I kept the singular conversion method and removed deprecated array handling:

impl From<Method> for AllowMethods {
    fn from(method: Method) -> Self {
        Self::exact(method) // Single-item conversion
    }
}

// Removed deprecated array-based impl:
impl<const N: usize> From<[Method; N]> for AllowMethods {
    fn from(arr: [Method; N]) -> Self {
        #[allow(deprecated)] // Can be changed when MSRV >= 1.53
        Self::list(array::IntoIter::new(arr))
    }
}

This simplifies the code, reduces duplication, and removes no longer necessary #[allow(deprecated)] annotations.
🐱 🧈