Allow server administrators to specify a custom piped log processor instead of splitlogs, similar to the existing ability to use a custom dnsadmin

It's already possible to use an alternative dnsadmin application, I'd like to also be able to specify an alternative application instead of /usr/local/cpanel/bin/splitlogs when using Apache Piped Logs. Currently there's no way to do this short of either:

1) Renaming /usr/local/cpanel/bin/splitlogs and placing the alternative there instead

2) Editing /usr/local/cpanel/Cpanel/AdvConfig/apache.pm to alter the hardcoded /usr/local/cpanel/bin/splitlogs paths to the alternative

Neither option is really feasible for production use as both are likely to be undone by a cPanel update, and putting the changes back in place via postupcp or similar is awfully dirty at best.

The current splitlogs implementation already supports a config file (/var/cpanel/conf/splitlogs.conf) for the maxopen/buffer settings - it seems entirely feasible for it to also allow specifying an alternative to /usr/local/cpanel/bin/splitlogs.

To that end I've written a small and easily-reviewed patch (attached) for Cpanel/AdvConfig/apache.pm that adds support for a new splitlogs.conf setting named 'app'. That setting specifies which executable to run, and defaults to '/usr/local/cpanel/bin/splitlogs' so the existing behaviour is unchanged. I don't believe any UI updates are necessary (at least, I can't find any existing UI to adjust the existing maxopen/buffer settings in 11.34.0.9)

All feedback appreciated, thanks for reading!