Fix/update default log-level handoff for databricks labs tools

[asnare]

Changes

This PR updates log-level handoff to the labs tools: they expect disabled instead of the default (WARN) if the user didn't explicitly specify a log-level.

Why

For various historical reasons, the labs tools were written with a default of INFO in mind and use this if the user doesn't explicitly provide a log-level when running a command. Prior to #2213 we used to receive disabled and it all worked as intended because the tools checked for this and could default to INFO themselves when it was detected.

However since #2213 the tools receive warn if the user didn't specify anything, and the tools can't distinguish between explicit --log-level=WARN and the default situation. This has lead to confusion amongst our users (and the FE teams involved) because suddenly the tool output changed.

With this change we're effectively reverting to the pre-#2213 behaviour which allows the labs tools to default to INFO while still respecting --debug, --log-level and DATABRICKS_LOG_LEVEL.

Tests

Table-driven tests check various scenarios, and also verify that there's no drift between the value we handoff and the log-level in use by the CLI. These changes have also been tested manually.

Caveats

One thing that's worth considering: it feels brittle that we have to mirror the logic from root/logger.go. The changes here are deliberately limited to just the labs area of the code, but if that constraint is relaxed there's probably a better way of handling it although it would mean changes outside the labs tree.

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Inputs:

• PR number: 4019
• Commit SHA: 10af613279bdf7dd532253daf2c99f492087f515

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