* Emit a `ɵɵcontrol` instruction in place of `ɵɵproperty` for property
  bindings named "control". This instruction cannot be chained, but is
  otherwise functionally equivalent.

* Upcoming changes will use the `ɵɵcontrol` instruction to bind a signal
  form field to a UI control (be it a native element or custom directive).

Move most of the implementation of the `Control` directive into core
framework instructions. This allows field state changes to be propagated
to their corresponding UI controls directly during execution of a
template update block, instead of relying on `effect()`s to synchronize
each change later during the update (and too late in the case of
required inputs).

* Define a private API in `@angular/core` for signal forms to implement:
  * `ɵControl` for the `Control` directive.
  * `ɵFieldState` for the control's associated `FieldState`.
* Emit specialized instructions when compiling a `[control]` binding:
  * `ɵɵcontrolCreate` sets up the `ɵControl` directive if present,
    determines whether it's bound to a native control element or a
    custom control component, and adds the appropriate event listeners
    to notify the `ɵFieldState` of UI changes.
  * `ɵɵcontrol` propagates changes from `ɵFieldState` properties to their
    corresponding UI control properties (in additional to binding the `control`
    property itself).