Allow `write.metadata.previous-versions-max` table property to be 0 for empty metadata logs

### Feature Request / Improvement

`write.metadata.previous-versions-max` is currently floored to 1:

https://github.com/apache/iceberg/blob/70b90330582e4023a097330620a3e63746b2375b/core/src/main/java/org/apache/iceberg/TableMetadata.java#L1801-L1807

so a table always retains at least one previous metadata file in the `metadata-log`.

I was a bit confused by this, because I don't see a concrete reason to disallow _empty_ metadata logs; I'd therefore like to know what folks think about permitting a value of 0 instead to enable this.

With [`write.metadata.delete-after-commit.enabled=true`](https://iceberg.apache.org/docs/latest/maintenance/#remove-old-metadata-files), this would then delete the superseded metadata file on every commit.

(My use case for this is from a REST catalog principle-based standpoint where an empty metadata log would allow metadata JSON to be "self-contained" and only reference its current snapshots, instead of indirectly reference snapshots in prior metadata files too)

### Query engine

None

### Willingness to contribute

- [x] I can contribute this improvement/feature independently
- [ ] I would be willing to contribute this improvement/feature with guidance from the Iceberg community
- [ ] I cannot contribute this improvement/feature at this time

Start in core/src/main/java/org/apache/iceberg/TableMetadata.java at the linked lines that floor write.metadata.previous-versions-max to 1. Trace the metadata-log retention behavior and its tests, including the interaction with write.metadata.delete-after-commit.enabled. Done means a value of 0 permits an empty metadata log and the described deletion behavior is covered by tests.

Written by the indexing model from the issue text.