Switch CLN channel locally until the last stage of the upgrade

[Monstrofil]

During upgrade, we should notify CLN about change of the OS version to update systemid file and the corresponding channel that system is subscribed to.

Before this patch we had logic like following:

• during preparation of overlayfs we switched channel to target_os_version globally (both for host machine and overlayfs)
• at later stages we reset it back to original

This caused problems: if upgrade process is inhibited or crashed, target os channel persisted on host machine and could lead to accidental upgrade on host machine.

This change instead uses local "channelOverride" rhn-client-tools option which changes the channel that we are subsribed to without notification of CLN, thus host machine and overlayfs now can be subscribed to different channels and do not interfire.

Smaller changes and their explanation:

• the way that we copy rhn files to overlayfs is not straightforward and works through TargetUserSpacePreupgradeTasks artifact, instead of copying them in multiple places (TargetUserSpacePreupgradeTasks, TargetUserSpaceUpgradeTasks, copy_files in overlaygen).
• cllicense check splitted into actors that check license and produce list of files to copy
• channel switch logic is not two-step process: during overlayfs creation we change subscription locally using up2date config, on FirstBootPhaseTag we notify CLN and change it permanently

[github-actions]

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