pal/uefi: Implement SystemTime::{MIN, MAX}

This commit implements `SystemTime::MIN` and `SystemTime::MAX` for the
UEFI platform.

UEFI has a weird way to store times, i.e. a very complicated struct.
The standard proclaims "1900-01-01T00:00:00+0000" to be the lowest
possible value and `MAX_UEFI_TIME` is already present for the upper
limit.

Author: cvengler

library/std/src/sys/pal/uefi/time.rs

@@ -66,6 +66,24 @@ impl Instant {
 }
 
 impl SystemTime {
+    #[unstable(feature = "time_systemtime_limits", issue = "none")]
+    pub const MAX: SystemTime = MAX_UEFI_TIME;
+
+    #[unstable(feature = "time_systemtime_limits", issue = "none")]
+    pub const MIN: SystemTime = SystemTime::from_uefi(r_efi::efi::Time {
+        year: 1900,
+        month: 1,
+        day: 1,
+        hour: 0,
+        minute: 0,
+        second: 0,
+        nanosecond: 0,
+        timezone: -1440,
+        daylight: 0,
+        pad1: 0,
+        pad2: 0,
+    });
+
     pub(crate) const fn from_uefi(t: r_efi::efi::Time) -> Self {
         Self(system_time_internal::from_uefi(&t))
     }