refactor: completely remove inclusive selection mode

Having inclusive mode change a few critical functions behind the sceans
is not a good way to share functionality. Basically every function is
broken in one or the other mode. So we remove it entirely and instead
will rely on different functions for different behaviors.

src/buffer/Selection.zig

@@ -9,8 +9,6 @@ end: Cursor = Cursor{},
 
 const Self = @This();
 
-pub const Style = enum { normal, inclusive };
-
 pub inline fn eql(self: Self, other: Self) bool {
     return self.begin.eql(other.begin) and self.end.eql(other.end);
 }