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

src/tool_cfgable.h

@@ -214,7 +214,7 @@ struct OperationConfig {
                         by using the default behavior for -o, -O, and -J.
                         If those options would have overwritten files, like
                         -o and -O would, then overwrite them. In the case of
-                        -J, this will not overwrite any files. */
+                        -J, this does not overwrite any files. */
     CLOBBER_NEVER, /* If the file exists, always fail */
     CLOBBER_ALWAYS /* If the file exists, always overwrite it */
   } file_clobber_mode;