feat(api): add nvim__redraw for more granular redrawing

Experimental and subject to future changes.
Add a way to redraw certain elements that are not redrawn while Nvim is waiting
for input, or currently have no API to do so. This API covers all that can be
done with the :redraw* commands, in addition to the following new features:
- Immediately move the cursor to a (non-current) window.
- Target a specific window or buffer to mark for redraw.
- Mark a buffer range for redraw (replaces nvim__buf_redraw_range()).
- Redraw the 'statuscolumn'.

src/nvim/api/keysets_defs.h

@@ -373,3 +373,17 @@ typedef struct {
   Boolean ignore_blank_lines;
   Boolean indent_heuristic;
 } Dict(xdl_diff);
+
+typedef struct {
+  OptionalKeys is_set__redraw_;
+  Boolean flush;
+  Boolean cursor;
+  Boolean valid;
+  Boolean statuscolumn;
+  Boolean statusline;
+  Boolean tabline;
+  Boolean winbar;
+  Array range;
+  Window win;
+  Buffer buf;
+} Dict(redraw);