vim-patch:8.2.0420: Vim9: cannot interrupt a loop with CTRL-C

Problem:    Vim9: cannot interrupt a loop with CTRL-C.
Solution:   Check for CTRL-C once in a while.  Doesn't fully work yet.
f1ec378b01

Vim9 test, commented out in this patch, is restored in patch 8.2.0421.
Vim9 tests were not ported over so skip the temporary change.

Vim should stop pushing broken commits on master.

src/nvim/misc1.c

@@ -1029,6 +1029,15 @@ void fast_breakcheck(void)
   }
 }
 
+// Like line_breakcheck() but check 100 times less often.
+void veryfast_breakcheck(void)
+{
+  if (++breakcheck_count >= BREAKCHECK_SKIP * 100) {
+    breakcheck_count = 0;
+    os_breakcheck();
+  }
+}
+
 /// os_call_shell() wrapper. Handles 'verbose', :profile, and v:shell_error.
 /// Invalidates cached tags.
 ///