[v26.1.x] iceberg: Push Parquest column stats to Iceberg manifests

[vbotbuildovich]

Backport of PR #30704

• Command: git cherry-pick -x 7f83353 b4e8232
• Commits backported: 2
• Conflicts resolved: 1
• Commits skipped (already on target): 0
• Backport branch: ai-backport-pr-30704-v26.1.x-1781219179

Conflict details

• 7f83353 (src/v/serde/parquet/writer.cc): only the two new file-level stat
  accumulation lines (file_value_count/file_column_size_bytes) were applied;
  the incoming bloom-filter block is a separate feature not present on v26.1.x
  and was omitted.
• 7f83353 (src/v/serde/parquet/column_writer.cc): the commit was built atop a
  stats-truncation feature (truncate_max/truncate_min,
  max_stats_truncate_length, is_utf8_string) that does not exist on v26.1.x.
  Adapted build_statistics() and flush_page() to the target's non-truncating
  bound logic, dropped the redundant _flushed_stats.record_value() calls in
  favor of merge(), added the _file_stats collector, and omitted the
  unrelated _bloom_filter member.
• 7f83353 (src/v/datalake/base_types.h): merged the new includes needed by
  per_column_stats (bytes, chunked_vector, serde envelope/rw); omitted
  base/format_to.h since v26.1.x's local_file_metadata still uses
  operator<< rather than format_to.
• 7f83353 (src/v/datalake/BUILD): merged the new base_types deps
  (base, bytes, container:chunked_vector, serde, serde:bytes) into the target's
  deps list.
• 7f83353 (src/v/datalake/coordinator/BUILD): kept both the target's
  //src/v/base dep and the incoming //src/v/bytes dep in
  iceberg_file_committer's implementation_deps.