Add the buildarr test-config command

[Callum027]

This PR implements the buildarr test-config command for testing configuration files.

The main differentiation from buildarr run --dry-run is that this checks the configuration as thoroughly as possible without communicating with remote instances (except when checking TRaSH-Guides metadata, in which case the latest metadata is downloaded from GitHub).

This allows local running outside of the *Arr stack network, ensuring a file is at least very likely to successfully load within Buildarr before deploying it.

This PR performs a refactor of the CLI command code to allow buildarr run and buildarr test-config to share as much code as possible, and changes a number of functions to operate on global state instead of using local variables, allowing multiple places to use the most up-to-date instance configurations (with TRaSH-Guides metadata rendered).

Information and debug logging has also been refactored and improved, moving all info logging out of functions (since those are likely to differ between types of commands), and adding additional debug logging output to make it easier to see the actual state Buildarr was in before an error occurs.

Related changes:

• Change the absolute path resolving function to not follow symbolic links (since targets can change between Buildarr runs in daemon mode)
• Remove temporary directories after TRaSH-Guides metadata rendering has completed