refactor!: rename "playground" => "dev" #23919

Problem:
"playground" is new jargon that overlaps with existing concepts:
"dev" (`:help dev`) and "view" (also "scratch" `:help scratch-buffer`) .

Solution:
We should consistently use "dev" as the namespace for where "developer
tools" live. For purposes of a "throwaway sandbox object", we can use
the name "view".
- Rename `TSPlayground` => `TSView`
- Rename `playground.lua` => `dev.lua`

scripts/gen_vimdoc.py

@@ -275,7 +275,7 @@ CONFIG = {
             'query.lua',
             'highlighter.lua',
             'languagetree.lua',
-            'playground.lua',
+            'dev.lua',
         ],
         'files': [
             'runtime/lua/vim/treesitter.lua',