Implement AccessPoint::last_seen, using procfs to get the boot time.

networkmanager/src/util.rs

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use time::OffsetDateTime;
+
+pub fn clock_boottime_to_time(time: i32) -> Option<OffsetDateTime> {
+	let boot_time = procfs::boot_time_secs()
+		.ok()
+		.and_then(|boot_time| i64::try_from(boot_time).ok())?;
+	OffsetDateTime::from_unix_timestamp(boot_time + time as i64).ok()
+}