fix(mdt): use native log format for file group initialization

[cshuo]

Describe the issue this Pull Request addresses

Closes #19311

When native log format is enabled, MDT file-group initialization still creates a legacy inline log containing an empty delete block. Empty file groups therefore do not have the native .log.hfile expected by the file-system view and may not be discovered before receiving records.

Summary and Changelog

• Create a zero-record native .log.hfile for each empty MDT file group when native log format is enabled.
• Store the instant time and writer schema in native footer metadata; the native log version is added by the footer metadata utility.
• Keep the existing empty delete-block initialization for legacy inline log format.
• Centralize both initialization paths in HoodieMetadataWriteUtils.
• Add a test that opens the generated HFile and verifies its footer metadata.

Impact

Empty MDT file groups are discoverable by the file-system view when native log format is enabled. There are no public API or configuration changes.

Risk Level

Low. The change is limited to initial empty MDT file-group creation, preserves the legacy inline path, and includes native HFile footer read coverage.

Documentation Update

None. There are no user-facing API or configuration changes.

Contributor's checklist

• Read through contributor's guide
• Enough context is provided in the sections above
• Adequate tests were added if applicable

[hudi-bot]

CI report:

• 026cdd5 UNKNOWN

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