Idle Connection Timeout Configuration

[stigglor]

Description

Allows connections in the pool to have a configurable idle timeout. This is required to ensure the idleTimeout < the configured clickhouse keep-alive timeout, preventing race conditions that lead to timeout errors reporting "unable to reach server".

• Adds configuration for connection pool idle connetion timeouts
• Decreases the default idle connection timeout to be < the default Clickhouse keep-alive timeout (10s)

Fixes: #92

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Checklist

• Linter passes correctly
• Add tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

Does this introduce a breaking change?

• Yes
• No

Further comments