Remove obsolete pgindent options --code-base and --build

Remove obsolete pgindent options --code-base and --build

Now that we have the sources for pg_bsd_indent in our code base these
are redundant.

It is now required to provide a list of files or directories to pgindent,
either by using --commit or on the command line. The equivalent of
previously running pgindent with no parameters is now `pgindent .`

Some extra checks are also added. duplicate files in the file list are
skipped, and there is a warning if no files are specified.

If the --commit option is used, the script now chdir's to the source
root, as git always reports files relative to that. (Fixes a gripe from
Justin Pryzby)

Reviewed by Tom Lane

Discussion: https://postgr.es/m/842819.1676219054@sss.pgh.pa.us