tree-wide: make parse_proc_cmdline() strip "rd." prefix automatically

tree-wide: make parse_proc_cmdline() strip "rd." prefix automatically

This stripping is contolled by a new boolean parameter. When the parameter
is true, it means that the caller does not care about the distinction between
initrd and real root, and wants to act on both rd-dot-prefixed and unprefixed
parameters in the initramfs, and only on the unprefixed parameters in real
root. If the parameter is false, behaviour is the same as before.

Changes by caller:
log.c (systemd.log_*):      changed to accept rd-dot-prefix params
pid1:                       no change, custom logic
cryptsetup-generator:       no change, still accepts rd-dot-prefix params
debug-generator:            no change, does not accept rd-dot-prefix params
fsck:                       changed to accept rd-dot-prefix params
fstab-generator:            no change, custom logic
gpt-auto-generator:         no change, custom logic
hibernate-resume-generator: no change, does not accept rd-dot-prefix params
journald:                   changed to accept rd-dot-prefix params
modules-load:               no change, still accepts rd-dot-prefix params
quote-check:                no change, does not accept rd-dot-prefix params
udevd:                      no change, still accepts rd-dot-prefix params

I added support for "rd." params in the three cases where I think it's
useful: logging, fsck options, journald forwarding options.