Drop file_checksum column from xray_reports table

As part of #479185 (closed), we are removing the xray_reports.file_checksum database column.

This issue drops the file_checksum column from the xray_reports table, following a multi-release approach for safe column removal.

It's the second step in a three-phase process:

  1. Ignoring the column (release M) - addressed with !169920 (merged) in %17.6
  2. Dropping the column (release M+1) - [%17.7]
  3. Removing the ignore rule (release M+2) - [%17.8] (issue)
Edited by Shola Quadri