Toggle cooldown swipe edge

[Neidunkt]

Summary

This PR adds the following functionalities:

1. changing the opacity of buff, debuff and CC countdown/cooldown swipes
2. enabling/disabling the countdown/cooldown edge

The changes concern the Nameplate and Designer.

Motivation

Community and own interest in this functionality.

Implementation

• implementation is based on the main logic and implementation of existing systems
• adding a slider and toggle to the Designer via WidgetConfiguration
• depending on the settings, change auras in Designer (container) and Nameplate (auraFrame)
• set default values in Initialize and AddWidgetList
• adding locales enUS for the slider and checkbox

Testing

• Tested on Live Retail server 12.0.0.65560 EU
• Reload UI, clearing SavedVariables

Screenshots
Usual behaviour (default):

Hiding Edge:

0 Swipe Opacity: