console/logging: uart: Device Idle Power Management

[JordanYates]

These two patches allow the console and logging UART backends to coexist with 'Device Idle Power Management'.
An application can enable idle power management on the UART backend with device_pm_enable and no longer need to worry about the UART hardware being enabled when it does not need to be.

Relevant code is only run when the power management hardware has been manually enabled.

The console request/release code is less efficient than the corresponding logging request/release code as the console output function operates on single bytes. There are 3 options to mitigate this:

1. Don't enable idle power management
2. The application can manually call device_pm_get_sync and device_pm_put_sync before large numbers of prints
3. printk can be routed through the more efficient logging implementation via CONFIG_LOG_PRINTK

[JordanYates]

After reading through some other idle power management issues for tangential reasons, I am not sure that device_idle_pm usage is actually wanted in tree.
#24653
@pabigot Do you have any further thoughts on this?

[pabigot]

I don't think we want to introduce uses of device_pm_{put,get} because that API was never used in-tree and everything in power management is changing anyway. There's been agreement (on slack) from the folks who introduced it that it could be removed at some point.

I have a use-case for disabling UART when not needed, but it needs API changes to allow the user to say "I may be receiving something; leave this active" vs "I only ever use this for transmit, shut it down when there's nothing pending." Right now the only way to do that, for drivers that support it, is removing the configuration of the RX pin. It should be more general so drivers can self-control power based on their current state. (This still should be coordinated with application control of whether that can happen.).

Also it may be necessary to clarify the required behavior of things like uart_poll_out, which right now can return before the character has actually been transmitted (making it difficult to know when it's safe to turn off the device).

I would prefer to start with API extensions.

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