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