Core: Enable re-partitioning of old spec data files.

### Feature Request / Improvement

**Problem**:
How to efficiently and reliably repartition only the data files belonging to the old partition specification so they conform to the new partition specification, without unnecessarily rewriting or impacting data files already written using the new spec?

**Example**:
Suppose we have evolved the table's partition specification by adding a new partition field, day, on top of an existing field, month. After few months, we want to re-partition all the old month data files to follow partitioning by day. Currently if those files are already of desired data sizes, they won't get picked up and thus will remain partitioned by old spec only.

**Explored solution using existing code and feature flags:**

As our use case is to rewrite the old partition spec data files to new spec data files, we have to use rewrite-all=true as rewrite job will skip the files which are already of desired size for example (512 MB by default) or if only one file per group rewrite but we would still need to rewrite them to desired spec.
Based on a suggestion by @pvary on an old PR #https://github.com/apache/iceberg/pull/12083#issuecomment-2751808447 and looking at the current code, I thought we can use filters to filter only the old data files after applying rewrite-all=true based on some column values for example timestamp( month <=2025-06) for rewriting. To efficiently rewrite a huge number of data files we have to also use partial-progress.enabled and partial-progress.max-commits such that if job fails half way we don't need to start from scratch.

**Why this won't work?**

Suppose there are so many files to rewrite and jobs fail half way. When we rerun using the same filter, it will again pick up the same files even if we have rewritten suppose 50% of files successfully. We can somehow improve the filter to pick only old files after every iteration but it puts a lot of work on end-user as currently we can't filter data files based on the spec ID.

**Suggested code change**

Based on above reasons, I suggest to enable this use case using this new flag rewrite-partition-spec-mismatch and partial-progress.enabled.

### Query engine

None

### Willingness to contribute

- [ ] I can contribute this improvement/feature independently
- [x] 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 by tracing the existing rewrite-all and partial-progress options in the Iceberg rewrite workflow; the issue does not name specific files or tests. Define completion as rewriting only files whose partition spec differs from the current spec, leaving matching files untouched, while allowing reruns to avoid already rewritten files.

Written by the indexing model from the issue text.