libzfs: add keylocation=https://, backed by fetch(3) or libcurl

Add support for http and https to the keylocation properly to
allow encryption keys to be fetched from the specified URL.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Issue #9543
Closes #9947
Closes #11956

contrib/dracut/90zfs/module-setup.sh.in

@@ -60,6 +60,11 @@ install() {
 		# Fallback: Guess the path and include all matches
 		dracut_install /usr/lib*/gcc/**/libgcc_s.so*
 	fi
+	if [ @LIBFETCH_DYNAMIC@ != 0 ]; then
+		for d in $libdirs; do
+			[ -e "$d"/@LIBFETCH_SONAME@ ] && dracut_install "$d"/@LIBFETCH_SONAME@
+		done
+	fi
 	dracut_install @mounthelperdir@/mount.zfs
 	dracut_install @udevdir@/vdev_id
 	dracut_install awk