Werk #14606: Agent Bakery: Optionally log to dedicated logfile

It's now possible to activate logging for the agent bakery. When activated at Global Settings - Setup - Agent bakery logging, the agent bakery will log messages to ~/var/log/agent_bakery.log, with the selected loglevel. This is applies equally to bakery jobs invoked via GUI or via command line.

Without activated logging, baking details are still available on the command line when baking with command cmk --bake-agents -v as a site user. Also, when baking on the GUI, on failure, error details are propagated to the executing background job as they already used to be.

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