Support .NET 10 MemoryExtensions.Contains with equality comparer in EF 8 and 9

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Because of the first-class spans feature in C# 14, MemoryExtensions.Contains gets resolved instead of Enumerable.Contains; we reacted to this in EF Core and backported the fix to EF 8 and 9.

However, #35547 tracked an additional issue around the new overload of MemoryExtensions.Contains, which has an optional comparer parameter, and gets resolved with C# 14. This was fixed for EF 10 (#35547), but was not backported to EF 8 and 9 (which we don't test with .NET 10 / C# 14). So to fully support C# 14 with EF 8 and 9, we need to backport #35547 from EF 10 to those releases as well.

Thanks to @ChrisJollyAU for figuring this out (dotnet/runtime#109757 (comment)) and to @CypherPotato for reporting in dotnet/runtime#109757 (comment).

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It seems that this bug is triggered specifically when Contains is invoked over an array of enums - the enum somehow causes the .NET 10 MemoryExtensions.Contains overload to be resolved which accepts a comparer.

Minimal repro

await using var context = new BlogContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

// Fails:
_ = await context.Blogs.Where(b => new SomeEnum[] { SomeEnum.One, SomeEnum.Too }.Contains(b.SomeEnum)).ToListAsync();

// Works:
// _ = await context.Blogs.Where(b => new[] { 1, 2, 3 }.Contains(b.Id)).ToListAsync();

// Works:
// _ = await context.Blogs.Where(b => MemoryExtensions.Contains(new[] { 1, 2, 3 }, b.Id)).ToListAsync();

// Fails:
// _ = await context.Blogs.Where(b => MemoryExtensions.Contains(new[] { 1, 2, 3 }, b.Id, comparer: null)).ToListAsync();

public class BlogContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer("Server=localhost;Database=test;User=SA;Password=Abcd5678;Connect Timeout=60;ConnectRetryCount=0;Encrypt=false")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();
}

public class Blog
{
    public int Id { get; set; }
    public SomeEnum SomeEnum { get; set; }
}

public enum SomeEnum { One, Too }