Lambdas in array initializers not checked in nullable walker

[gafter]

Lambda expressions in an array initializer are not checked against the new target type of the lambda expression. Instead, the type from initial binding is used, and (improperly) feeds into inference.

        [Fact, WorkItem(35302, "https://github.com/dotnet/roslyn/issues/35302")]
        public void CheckLambdaInArrayInitializer_02()
        {
            var source =
@"using System;

class C
{
    static void G(object? o, string s)
    {
        if (o == null) return;
        var f = M(o);
        _ = f /*T:System.Func<object!>!*/;
        var fa3 = new[] {
            f,
            () => null, // 1
            () => {
                    s = null; // 2
                    return null; // 3
                },
            };
        _ = fa3 /*T:System.Func<object!>![]!*/;
        fa3[0]().ToString();
    }
    static Func<T> M<T>(T t) => () => t;
}
";
            var comp = CreateCompilation(new[] { source }, options: WithNonNullTypesTrue());
            comp.VerifyTypes();
            comp.VerifyDiagnostics(
                // (12,19): warning CS8603: Possible null reference return.
                //             () => null, // 1
                Diagnostic(ErrorCode.WRN_NullReferenceReturn, "null").WithLocation(12, 19),
                // (14,25): warning CS8600: Converting null literal or possible null value to non-nullable type.
                //                     s = null; // 2
                Diagnostic(ErrorCode.WRN_ConvertingNullableToNonNullable, "null").WithLocation(14, 25),
                // (15,28): warning CS8603: Possible null reference return.
                //                     return null; // 3
                Diagnostic(ErrorCode.WRN_NullReferenceReturn, "null").WithLocation(15, 28));
        }

There may be similar issues in method type inference, ?:, switch expressions, etc.

[gafter]

A couple of tests are skipped on this issue.