Changes `parsedErrors` to a `linkedSignal` based on the model value.
This ensures that the parse errors are reset if the model changes from
outside the control.

Integrates native inputs with the new parseErrors API so that they can
report parse errors when the user types an un-parsable value (e.g. "42e"
in a number field).

When a user types an un-parsable value, the model does not update. It
retains its previous value and a parse error is added for the control
that received the un-parsable value.

Supports binding `null` to a `<input type=number>`.

- Binding in `null` clears the input
- Binding in `NaN` also clears the input
- When the user clears the input, the model is set to `null`
- The model is _never_ set to `NaN` based on user interaction. It is
  either set to `null` if the user cleared the input, or is unchanged
  and a parse error added if the user entered an invalid number like
  "42e"

native controls and custom controls (via transformedValue) use similar
parsing logic but it needs to be hooked up differently. This commit
extracts the common bits into a shared piece.