Add Span overloads to System.Numerics.Vectors

[C-xC-c]

Fixes #25608

[ghost]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[ghost]

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Issue Details

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Fixes #25608

Author:	C-xC-c
Assignees:	-
Labels:	area-System.Numerics, new-api-needs-documentation
Milestone:	-

[GrabYourPitchforks]

@tannergooding You've mentioned in the past that some SIMD instructions (specifically, instructions that access float* or double*) have some weirdness when it comes to alignment. Is using Read/WriteUnaligned in these code paths likely to have noticeable perf impact?

[tannergooding]

Is using Read/WriteUnaligned in these code paths likely to have noticeable perf impact?

It shouldn't on modern CPUs. The only real impact should be if it crosses a cache line or page boundary and then only if you repeatedly do that in a hot loop.

[tannergooding]

CC. @pgovind, can you give a quick review so we can merge?

[pgovind]

LGTM!

[tannergooding]

Thanks for the contribution!