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

docs/examples/httpput-postfields.c

@@ -32,7 +32,7 @@
 
 static const char olivertwist[] =
   "Among other public buildings in a certain town, which for many reasons "
-  "it will be prudent to refrain from mentioning, and to which I will assign "
+  "it is prudent to refrain from mentioning, and to which I assign "
   "no fictitious name, there is one anciently common to most towns, great or "
   "small: to ___, a workhouse; and in this workhouse was born; on a day and "
   "date which I need not trouble myself to repeat, inasmuch as it can be of "