When an `NgModel` is created within a `form`, it receives an `NgControl` based on its `name`, but
the control doesn't get swapped out if the name changes. This can lead to problems if the `NgModel`
is part of an `ngFor`, because the name can change based on its position in the list and a new
control can be defined with the same name, leading us to having multiple directives pointing to
the same control. For example, if we start off with a list like :
```
[0, 1, 2]; -> [NgModel(0), NgModel(1), NgModel(2)]
```
Then we remove the second item:
```
[0, 2]; -> [NgModel(0), NgModel(2)]
```
And finally, if we decide to add an item to the end of the list, we'll already have a control for
index 2, causing the list to look like:
```
[0, 2, 3]; -> [NgModel(0), NgModel(2), NgModel(2)]
```
These changes fix the issue by removing the old control when the `name` of the directive changes.
Fixes#38465.
Fixes#37920.
PR Close#40459
ebf2fc5224