feat(terminal)!: make 'belloff' and 'visualbell' apply to terminal bell (#30859)

vim-patch:8.2.4744: a terminal window can't use the bell
vim-patch:8.2.4745: using wrong flag for using bell in the terminal

BREAKING CHANGE: Bells from :terminal are now silent by default, unless
'belloff' option doesn't contain "term" or "all".

src/nvim/option_vars.h

@@ -403,7 +403,8 @@ EXTERN unsigned bo_flags;
 #define BO_REG    0x8000
 #define BO_SH     0x10000
 #define BO_SPELL  0x20000
-#define BO_WILD   0x40000
+#define BO_TERM   0x40000
+#define BO_WILD   0x80000
 
 EXTERN char *p_bsk;             ///< 'backupskip'
 EXTERN char *p_breakat;         ///< 'breakat'

src/nvim/options.lua

@@ -598,6 +598,7 @@ return {
         separated list of items. For each item that is present, the bell
         will be silenced. This is most useful to specify specific events in
         insert mode to be silenced.
+        You can also make it flash by using 'visualbell'.
 
         item	    meaning when present	~
         all	    All events.
@@ -621,6 +622,7 @@ return {
         register    Unknown register after <C-R> in |Insert-mode|.
         shell	    Bell from shell output |:!|.
         spell	    Error happened on spell suggest.
+        term	    Bell from |:terminal| output.
         wildmode    More matches in |cmdline-completion| available
         	    (depends on the 'wildmode' setting).
 

src/nvim/optionstr.c

@@ -73,7 +73,8 @@ static char *(p_bg_values[]) = { "light", "dark", NULL };
 static char *(p_bkc_values[]) = { "yes", "auto", "no", "breaksymlink", "breakhardlink", NULL };
 static char *(p_bo_values[]) = { "all", "backspace", "cursor", "complete", "copy", "ctrlg", "error",
                                  "esc", "ex", "hangul", "insertmode", "lang", "mess", "showmatch",
-                                 "operator", "register", "shell", "spell", "wildmode", NULL };
+                                 "operator", "register", "shell", "spell", "term", "wildmode",
+                                 NULL };
 // Note: Keep this in sync with briopt_check()
 static char *(p_briopt_values[]) = { "shift:", "min:", "sbr", "list:", "column:", NULL };
 // Note: Keep this in sync with diffopt_changed()

src/nvim/terminal.c

@@ -1178,9 +1178,10 @@ static int term_settermprop(VTermProp prop, VTermValue *val, void *data)
   return 1;
 }
 
+/// Called when the terminal wants to ring the system bell.
 static int term_bell(void *data)
 {
-  ui_call_bell();
+  vim_beep(BO_TERM);
   return 1;
 }