Stop using deprecated as tracking flag, minor fixes

[yuliannabn]

Context

Due to the deprecated flag determining if the node is being tracked or not, a node can be incorrectly flagged as non-deprecated when its true state is not yet known. This happens whenever a deprecated node (which is deleted from the tracking list) is found again, and due to being now seen as a "new node", the deprecation flag is changed to false (default) regardless of its previous state, making it temporally (and incorrectly) non-deprecated until time is exhausted.
A workaround to this can be to keep its previous deprecation state unless proven otherwise, and use another column to determine if the node is currently being tracked or not.

Tasks

• Correct first_connected to use coalesce to store it. Currently, first_connected is not being saved at all.
• last_error column -> Make this column include ErrorNone.
• New column is_tracked -> boolean, use to track if the node is in the watchlist or not.
• deprecated -> do not change unless needed.
• Print current deprecation time in startup logs.