Expose toggle method for the snackbar component

[IvayloG]

Description

By design, the snackbar exposes only Show&Hide methods.
Having a slim API is nice for maintenance however, missing Toggle method results in both:

1. Unconsistend API through the frameworks as it is exposed in igniteui-angular
2. From AB/CodeGen perspective: Can't reuse the existing toggle functionality and simply use the same target(button) to generate a toggle functionality.

Steps to reproduce

1. Open AB
2. Add a button and a snackbar.
3. Set OnClick for the button and the snackbar as a target.
4. Observe both click handlers

Result

For both toggle scenarios(snackbar OR a button as origin), the following could not be achieved as Toggle() is not yet implemented.

Blazor*
	<IgbButton @onclick="@(e => Snackbar?.Toggle())" @ref="Snackbar">Button</IgbButton>
	<IgbSnackbar Action="e => Snackbar?.Toggle()" @ref="Snackbar">Message</IgbSnackbar>

@code {
    private IgbSnackbar Snackbar;
}

Expected result

• Having a toggle method exposed, the above pseudo-code will actually work.

• Having in mind Snackbar toggling itself could be argued as it could only be closed and not open by itself, triggering toggle from outside (ex. a button) is a pretty main scenario.