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

lib/cf-h2-proxy.c

@@ -157,7 +157,7 @@ static void h2_tunnel_go_state(struct Curl_cfilter *cf,
     ts->state = new_state;
     /* If a proxy-authorization header was used for the proxy, then we should
        make sure that it is not accidentally used for the document request
-       after we have connected. So let's free and clear it here. */
+       after we have connected. Let's thus free and clear it here. */
     Curl_safefree(data->state.aptr.proxyuserpwd);
     break;
   }