Timestamps should not rely on board initialization time

[dbendele]

Describe the bug
Custom devices running at the same time have timestamps (returned by hardware) that are 20+ seconds different. This can make it difficult to correlate and order messages.

To Reproduce
Steps to reproduce the behavior:

1. Add two instances of the custom device
2. Deploy and Run
3. Note that scheduled messages have different receive timestamps that differs by about the time it takes to initialize a card.

Expected behavior
I would expect messages received at the same time to bear the same timestamp.

Screenshots

Desktop (please complete the following information):

• OS: Linux RT
• Version:

Additional context
Add any other context about the problem here.

[Karl-G1]

Converting to an 'enhancement'. We have not explicitly tested external timing sources, and the current behavior of message Timestamp channels is based on the fact the cards timers are starting from zero. Because the cards are not initialized at the same time, they will reset and start counting roughly 20-30 seconds apart.

If users want to correlate Timestamp values to a system time, they can reference the Absolute Time channel in System Channels and calculate the offset based on the Timestamps. Logging this with Embedded Data Logger over time would have a persistent record in case they drift.