Provide option to let query run as long as necessary

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## What did you do?

- I executed a COPY query for AWS Redshift which takes a very long time.

## What did you expect to happen?

- I expected Postico to wait until the query completed.

## What actually happened?

- The app closed the connection after 300 seconds, which cancelled the query

## What software versions are you using?

Postico version:
1.4.2 (2845)

macOS version:
10.13.6 (17G65)

PostgreSQL version:
PostgreSQL 8.0.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3), Redshift 1.0.3906

The issue concerns long-running AWS Redshift COPY queries and a connection timeout after 300 seconds. Start by locating the query execution and timeout handling in the Postico codebase, then inspect the existing comments or tests around connection cancellation. Done means users can choose to let a query run beyond the current limit without the connection being closed.

Written by the indexing model from the issue text.