renderer: added cursor style and visibility uniforms

Specifically:
iCurrentCursorStyle
iPreviousCursorStyle
iCurrentCursorVisible
iPreviousCursorVisible

Visibility calculated and updated independently from the typical cursor
unifrom updates to preserve cursor style even when not in the viewport
or set to be hidden

src/renderer/cursor.zig

@@ -15,7 +15,7 @@ pub const Style = enum {
     lock,
 
     /// Create a cursor style from the terminal style request.
-    pub fn fromTerminal(term: terminal.CursorStyle) ?Style {
+    pub fn fromTerminal(term: terminal.CursorStyle) Style {
         return switch (term) {
             .bar => .bar,
             .block => .block,