Deprecate Object Store config outside gdk.yml

Alessio Caiazzarequested to merge
ac-os-gdk.yml-ssot into main

This commit allows deprecating configuration values read from files.

Reading config from a file will write a warning message to STDERR informing of the deprecation

WARNING: object_store_enabled is deprecated.
WARNING: Write 'false' as object_store.enabled in gdk.yml and remove object_store_enabled to get rid of this message

Related to #658 (closed)

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