[Obsolete]: Remove SetTheme method from ThemeManager

[giduac]

Describe the bug
In ThemeManager the method SetTheme is obsolete and has to be removed in V100

        /// <summary>
        /// Sets the theme.
        /// </summary>
        /// <param name="themeName">Name of the theme.</param>
        /// <param name="manager">The manager.</param>
        [Obsolete("Deprecated and will be removed in V100. Replace this with calls to ApplyTheme( . . . )")]
        public static void SetTheme(string themeName, KryptonManager manager) =>
            //TODO V100 Remove SetTheme method
            ApplyGlobalTheme(manager, GetThemeManagerMode(themeName));

[Smurf-IV]

Note: Please check all the other instances of the Obsolete usage in the alpha branch as well.

[giduac]

Note: Please check all the other instances of the Obsolete usage in the alpha branch as well.
@Smurf-IV , @PWagner1 && @Ahmed-Abdelhameed

Please have a look the search results for 'Obsolete' and respond with what can be taken out.
After that this call can be altered to take them out all at once.