Modify schema to wikitext_raw_rc2.

In this MR we:

• Introduce column row_visibility_last_update to keep track of visibility changes separate from other page updates.
• Introduce an errors column that should let us identify event stream errors, if any.
• Change partitioning to PARTITIONED BY (wiki_db, months(revision_timestamp)), which will alleviate inode pressure on the HDFS Namenode.
• Explicitly make the table an Iceberg v2 table, so that, in the event we need to do Iceberg merge-on-read, we can.

Bug: T340863