Fixing idle issue and improving debug logging

[benc-db]

Hopefully resolves #647

Description

Customers with high concurrency on SQL Warehouses have been hitting an issue where they see 'Remote disconnected' as the error. It appears somewhere in the stack, connections that have been idle for 180+s hit this issue when we attempt to reuse them. This PR has the following:

• Move default time for considering a connection stale to 60s (most of the benefit of reusing connections comes from having many quick operations anyway, since the overhead of creating and closing connections is sub-second).
• Significant refactoring of logging to improve clarity and consistency in debug logs
• I noticed that BearerAuth was invoking the header factory on create rather than call, which I believe is what was causing Authentication Issue: Polling Python Job Status - Access Token Cached on Creation #647

Checklist

I should probably add tests for the logging, but I will hold that for when I bring this code into 2.0.0 branch (to reduce the significant pain that will already be).

• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change to the "dbt-databricks next" section.