Create stable IDs for all components

[vladitasev]

We already have:

	/**
	 * Use this method in order to get a reference to element in the shadow root of a web component
	 * @public
	 * @param {String} refName Defines the name of the stable DOM ref
	 */
	getStableDomRef(refName) {
		return this.getDomRef().querySelector(`[data-ui5-stable=${refName}]`);
	}

in UI5Element.js. Example usage: data-ui5-stable="{{this.stableDomRef}}"

Add stable IDs to all relevant parts of the components so that tests can easily access them without the risk of breaking after a refactoring. Document all stable IDs for each component.

[vladitasev]

Notes:

• should work for static area too
• document all such stable IDs in the class description as a start.

[vladitasev]

Not relevant any more

• no static area
• many internal elements already have parts
• there are already cypress utils for testing that help with this