hibernate-resume-generator: wait "infinitely" for the resume device

This makes changes similar to the parent commit, but for hibernate-resume-generator.
If resume= is specified on the kernel command line, we'll set JobRunningTimeoutSec=0
for the device. This matches what we do for the root device.

In practice, other timeouts will take effect. For example dracut tries (and
fails :[ ) to start dracut-emergency.service after some time.

Fixes #7242, https://bugzilla.redhat.com/show_bug.cgi?id=1705522.

(cherry picked from commit ff757c9d)
(cherry picked from commit bb598b56)
(cherry picked from commit 1a5428c2)