allow using cosl.coordinated_workers.S3ConnectionInfo outside of tempo-loki-mimir

Bug Description

Right now attempting to import that module from outside the HA charms (e.g. Parca) will result in import errors because of the check-charm-libs-installed thing we do on import.

we should either refactor cosl to run that check on-demand rather than on import, or lift anything that needs not be under that check outside of the coordinated_workers module so other charms can use them without ugly workarounds.

To Reproduce

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Environment

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Relevant log output

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Additional context

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