Add PDF417 barcode support

Rather than implementing this ourselves (1+k lines of code, several large
data tables), this uses ZXing as an (optional) dependency, making the
implementation straightforward.

ZXing as a dependency is also interesting as it contains support for
all other formats as well, potentially allowing us to use it instead of
the other external dependencies. ZXing is larger than those, but it's
also used in other KDE code already, unlike qrencode and libdmtx.
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passed android_qt515 #146992
Linux

00:00:18

passed freebsd_qt515 #146993
FreeBSD

00:00:29

passed suse_tumbleweed_qt515 #146991
Linux

00:00:33