refactor(defaults)!: change default 'commentstring' value to empty (#22862)

runtime/doc/news.txt

@@ -66,6 +66,8 @@ The following changes may require adaptations in user config or plugins.
   change is that language-specific highlight groups need to be renamed from
   `@foo.help` to `@foo.vimdoc`.
 
+• The default value of 'commentstring' is now empty instead of "/*%s*/".
+
 ==============================================================================
 NEW FEATURES                                                    *news-features*
 

runtime/doc/options.txt

@@ -1390,7 +1390,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	insert a space.
 
 					*'commentstring'* *'cms'* *E537*
-'commentstring' 'cms'	string	(default "/*%s*/")
+'commentstring' 'cms'	string	(default "")
 			local to buffer
 	A template for a comment.  The "%s" in the value is replaced with the
 	comment text.  Currently only used to add markers for folding, see

runtime/doc/vim_diff.txt

@@ -34,6 +34,7 @@ Defaults					            *nvim-defaults*
 - 'backspace' defaults to "indent,eol,start"
 - 'backupdir' defaults to .,~/.local/state/nvim/backup// (|xdg|), auto-created
 - 'belloff' defaults to "all"
+- 'commentstring' defaults to ""
 - 'compatible' is always disabled
 - 'complete' excludes "i"
 - 'directory' defaults to ~/.local/state/nvim/swap// (|xdg|), auto-created

runtime/ftplugin/c.lua

@@ -0,0 +1 @@
+vim.bo.commentstring = '/*%s*/'

runtime/ftplugin/calender.lua

@@ -0,0 +1 @@
+vim.bo.commentstring = '/*%s*/'

runtime/ftplugin/css.lua

@@ -0,0 +1 @@
+vim.bo.commentstring = '/*%s*/'

runtime/ftplugin/indent.lua

@@ -0,0 +1 @@
+vim.bo.commentstring = '/*%s*/'

runtime/ftplugin/xdefaults.lua

@@ -0,0 +1 @@
+vim.bo.commentstring = '/*%s*/'