Add option to disable concurrency checking at the SaveChanges level

[rafaelvascc]

On our application we added optimistic concurrency using the [ConcurrencyCheck] annotation on our model classes. It is working fine, but there are some very specific cases where we would like to force an update without doing concurrency checking (yes, we know the risks).

We would like a built-in solution on EF Core DbContext that ignores concurrency checking for some entities when calling SaveChanges. Something like:

_context.IgnoreConcurrencyChecking(entity);
_context.SaveChanges();
//No DbConcurrencyException just a forced updated

Thanks.

[ajcvickers]

Note for triage: very similar to #10443

[AndriySvyryd]

#10443 is at the model level, while this one is at the SaveChanges level. It makes sense to track them separately.

Added to the epic.

[rafaelvascc]

Thanks for having the time to take a look into it guys.

[ascott18]

An opt-in would also be nice: the ability for a specific save operation to specify optimistic concurrency for some set of fields that are not otherwise declared for optimistic concurrency on the model.

_context.CheckConcurrency<Page>(p => new { p.ParentId, p.Order });
_context.SaveChanges();