Router: Time initialization fixes and cleanups

Most changes are relevant only if NTP is disabled or failed at startup.

- Require two peers that agree for transports to initialize time
- Briefly ban skewed peer when not initialized, so another peer will be the second sample
- Allow SSU2 to initialize time even for large skews
- Do not allow NTCP2 inbound to initialize time for large skews
- Disable SSU1 time initialization when SSU2 is enabled
- When SSU2 is disabled, allow SSU1 time initialization even for large skews
- Don't adjust to large inbound NTCP2 skews when not initialized
- Round time sent in NTCP2 DateTime block
- Adjust SSU2 skew for RTT
- Don't sort by absolute skew on SSU /peers tab so we can find median
- Only call System.currentTimeMillis() once in RouterClock.setOffset()
- Log tweaks

apps/routerconsole/java/src/net/i2p/router/web/helpers/UDPSorters.java

@@ -155,7 +155,7 @@ class UDPSorters {
     static class SkewComparator extends PeerComparator {
         @Override
         public int compare(PeerState l, PeerState r) {
-            long rv = Math.abs(l.getClockSkew()) - Math.abs(r.getClockSkew());
+            long rv = l.getClockSkew() - r.getClockSkew();
             if (rv == 0) // fallback on alpha
                 return super.compare(l, r);
             else