Web Console: Incorrect `QuestDB is not reachable` error on query errors

[insmac]

Some HTTP errors (i.e. 431 - Request header fields too large) are not supported correctly in the UI and fall under the "QuestDB is not reachable" umbrella, thus confusing user as to what's happening.

Steps to reproduce:

1. To see how a proper QuestDB is not reachable error should look in the UI, stop QuestDB while Web Console is opened, and try refreshing the table list.
2. Try a very large query, which exceeds the request header limit. A sample query is attached below:
   query_too_long (1).txt
3. Execute the above query and observe the error:

Desired workaround:

1. Only display "offline" errors only when a certain type of error is returned (i.e. 50x).
2. Display a request error in the UI.

[vicheanath]

• After I tried this query it also some conflict in date time UI
• For 431 - Request header fields too large I think it should be changed logic from the backend like split the large request to multiple time in one query