Improve CascadeSelect implementation for Accessibility

[mertsincan]

CascadeSelect's codebase has been completely overhauled for accessibility. In addition, some extra changes were made to the design based on user feedback.

Added Properties:

• optionDisabled: Property name or getter function to use as the disabled flag of an option, defaults to false when not defined.
• inputId: Identifier of the underlying input element.
• InputStyle: Inline style of the input field
• inputClass: Style class of the input field
• inputProps: Uses to pass all properties of the HTMLInputElement/HTMLSpanElement to the focusable input element inside the component
• panelStyle: Inline style of the overlay panel
• panelProps: Uses to pass all properties of the HTMLDivElement to the overlay panel inside the component.
• inputProps: Uses to pass all properties of the HTMLInputElement to the focusable input element inside the component
• panelStyle: Inline style of the overlay panel
• panelProps: Uses to pass all properties of the HTMLDivElement to the overlay panel inside the component.
• autoOptionFocus: Whether to focus on the first visible or selected element when the overlay panel is shown.
• searchLocale: Locale to use in searching. The default locale is the host environment's current locale.
• searchMessage: Text to be displayed in hidden accessible field when filtering returns any results. Defaults to value from PrimeVue locale configuration.
• selectionMessage: Text to be displayed in hidden accessible field when options are selected. Defaults to value from PrimeVue locale configuration.
• emptySelectionMessage: Text to be displayed in hidden accessible field when any option is not selected. Defaults to value from PrimeVue locale configuration
• emptySearchMessage: Text to display when filtering does not return any results. Defaults to value from PrimeVue locale configuration.
• tabindex: Index of the element in tabbing order.
• ariaLabel: Defines a string value that labels an interactive element.
• ariaLabelledby: Identifier of the underlying input element.