Improve client generation failure messages at the client level

[AntonOfTheWoods]

In certain circumstances where the reason is clearly known (e.g., trying to generate the client when there are tables that have FKs to unelectrified tables) the current message at the client level is:

...
Error: Error in connector: Error querying the database: Error querying the database: The server terminated the connection.
...

It would be a much nicer DX to have the message, which is clearly visible in the electric server logs, returned to the client so the developer can see without going looking for logs elsewhere.

[linear]

VAX-1834 Improve client generation failure messages at the client level