fix: Add core-site.xml when configuring HDFS connection

[sbernauer]

Description

Related to #525 (not sure if it fixes it)

We already know this was needed when e.g. enabling Kerberos on HDFS, so we would have needed this change in any case in the future.
Also this pulls in the defaultFS from the core-site.xml

Definition of Done Checklist

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1. Changes are OpenShift compatible
2. CRD changes approved
3. CRD documentation for all fields, following the style guide.
4. Helm chart can be installed and deployed operator works
5. Integration tests passed (for non trivial changes)
6. Changes need to be "offline" compatible

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1. Code contains useful comments
2. (Integration-)Test cases added
3. Documentation added or updated. Follows the style guide.
4. Changelog updated
5. Cargo.toml only contains references to git tags (not specific commits or branches)

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1. Feature Tracker has been updated
2. Proper release label has been added

[sbernauer]

Started https://ci.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/trino-operator-it-custom/111/

[maltesander]

LGTM!