badwords: rework exceptions, fix many of them

Also:
- support per-directory and per-upper-directory whitelist entries.
- convert badlist input grep tweak into the above format.
  (except for 'And' which had just a few hits.)
- fix many code exceptions, but do not enforce.
  (there also remain about 350 'will' uses in lib)
- fix badwords in example code, drop exceptions.
- badwords-all: convert to Perl.
  To make it usable from CMake.
- FAQ: reword to not use 'will'. Drop exception.

Closes #20886

scripts/badwords

@@ -17,6 +17,8 @@
 use strict;
 use warnings;
 
+use File::Basename;
+
 my @whitelist = (
     # ignore what looks like URLs
     '(^|\W)((https|http|ftp):\/\/[a-z0-9\-._~%:\/?\#\[\]\@!\$&\'\(\)*+,;=]+)',
@@ -99,16 +101,32 @@ sub highlight {
     my ($p, $w, $in, $f, $l, $lookup) = @_;
 
     my $c = length($p)+1;
-    my $ch = "$f:$l:$w";
+    my $ch;
+
+    my $dir = dirname($f);
+    $ch = $dir . "/" . "::" . $w;
     if($wl{$ch}) {
-        # whitelisted filename + line + word
+        # whitelisted dirname + word
         return;
     }
+    my $updir = dirname($dir);
+    if($dir ne $updir) {
+        $ch = $updir . "/" . "::" . $w;
+        if($wl{$ch}) {
+            # whitelisted upper dirname + word
+            return;
+        }
+    }
     $ch = $f . "::" . $w;
     if($wl{$ch}) {
         # whitelisted filename + word
         return;
     }
+    $ch = "$f:$l:$w";
+    if($wl{$ch}) {
+        # whitelisted filename + line + word
+        return;
+    }
 
     print STDERR  "$f:$l:$c: error: found bad word \"$w\"\n";
     printf STDERR " %4d | %s\n", $l, $in;