fix: fall back for Parquet datetime rebasing

[peterxcli]

Which issue does this PR close?

Closes #5010.

Rationale for this change

Native Parquet scans cannot currently apply Spark's legacy Julian/Gregorian rebasing safely before Parquet pruning, filters, and aggregates consume datetime values. This can produce incorrect results for files written by Spark 2.x or with legacy datetime or INT96 rebasing.

I want to merge this conservative fallback first to restore correctness with a small, low-risk change. The native implementation in #5047 should remain a follow-up and can restore native acceleration after its broader per-file rebasing behavior is reviewed.

What changes are included in this PR?

• Inspect Parquet footer metadata and configured read modes before converting a scan to Comet.
• Fall back to Spark when any input file may require legacy datetime or INT96 rebasing, or when metadata inspection fails.
• Remove the dead datetime-rebase configuration and the unused SparkParquetOptions.use_legacy_date_timestamp_or_ntz field.
• Update scan compatibility documentation and add regression coverage for the fallback.

How are these changes tested?

• make core
• git diff --check
• ./mvnw test -Dtest=none -Dsuites="org.apache.comet.parquet.ParquetReadV1Suite fallback for Parquet datetime rebasing" -Dscalastyle.skip=true

[peterxcli]

copied spec from https://github.com/apache/spark/blob/v4.1.2/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSourceUtils.scala#L130-L177