Create IPP Everywhere printer through IPP

[michaelrsweet]

Copied from Apple CUPS #5919

Update cupsd to support a "ppd-name" of "everywhere" to generate the PPD in the background:

• Update cupsd to use create_local_bg_thread in add_printer when "ppd-name" is "everywhere"
• Update lpadmin to not create PPD locally
• Update admin.cgi to not create PPD locally
• Update _ppdCreateWithIPP to copy the 128x128 icon as embedded data in PPD file.
• Update cupsd/load_ppd to copy the icon data to ServerRoot/icons/PRINTERNAME.png
• Update cupsd to expose printer icons from ServerRoot/icons

[zdohnal]

P.S. commit 68506ac broke test suite, we will need to investigate further.

[zdohnal]

This error appeared after the mentioned commit:

E [13/Jul/2021:12:30:21.337402 +0200] [cups-driverd] Unable to open \"/tmp/cups-zdohnal/share/model/everywhere\" - No such    file or directory

[zdohnal]

Error log from the test run - the error happens during serving CUPS-Get-PPD request which hasn't been migrated to support everywhere model.

Currently I'm not sure whether we want to migrate this operation for everywhere or not, and if we want, how to get the ppd, because cups-driverd works with files, and _ppdCreateFromIPP() returns only char array for now.

[michaelrsweet]

@zdohnal Not sure why I didn't catch this when I did testing, but fixed now:

[master 3a37c0d] Fix regression caused by change for Issue #201.

[zdohnal]

@michaelrsweet verified, tests are passing now. Thx!

[michaelrsweet]

Moving the printer icon stuff to 2.5.