[release/10.0] Fix UnsafeAccessor signature for byref struct this

[github-actions]

Backport of #122754 to release/10.0

/cc @AaronRobinsonMSFT @hez2010

Customer Impact

• Customer reported
• Found internally

This was reported twice by the community and fixed early in .NET 11. It wasn't backported to .NET 10 at the time.

Fixes #122678
Fixes #128806

Motivating example:

using System.Runtime.CompilerServices;

S<int> sInt32 = new();
Accessor<int>.M(ref sInt32);
Console.WriteLine("Int32 okay");

S<string> sString = new();
Accessor<string>.M(ref sString); // <- Will cause an A/V
Console.WriteLine("string okay");

public struct S<T>
{
    private void M() { }
}

public static class Accessor<T>
{
    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "M")]
    public static extern void M(ref S<T> s);
}

Regression

• Yes
• No

This was a latent issue found with generic support.

Testing

A test was added.

Risk

Low. This has been in .NET 11 for quite some time. Porting to .NET 10 due to additional customer impact.

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[JulieLeeMSFT]

@AaronRobinsonMSFT, please check test failures.

[AaronRobinsonMSFT]

@JulieLeeMSFT None of these are related. They seem to be have something to do with iOS apps and system resources.

[AaronRobinsonMSFT]

@JulieLeeMSFT I've checked and none of the failures appear related. I've just updated the base again.

[AaronRobinsonMSFT]

@JulieLeeMSFT or @steveisok This is as green as it can get. Please merge this in.

[JulieLeeMSFT]

/ba-g all known issues.