UnsafeRawBufferPointer and UnsafeMutableRawBufferPointer perform element-by-element scans in firstIndex(of: Element) and lastIndex(of: Element). It appears that these types should be amenable to some improvements, by using vectorized loops.

Motivation
UnsafeRawBufferPointer.firstIndex(of:) might be faster and/or more efficient with a specialized implementation.

Solution
Benchmarks should be created, and then implementations of the Collection customization points _customIndexOfEquatableElement() and _customLastIndexOfEquatableElement() should be investigated.

Alternatives considered
If no substantial improvements are found, then drop it. That fact should be documented so that someone else doesn't repeat this work in the future.