Address BBM classes AvoidSilentRescueExceptions todos

Context

Some time ago, a new cop was introduced to flag rescued exceptions in BBM job classes.

As the cop is quite stable now, we should fix the TODO files left in grace period.

The list of BBM classes to be fixed are:

• lib/gitlab/background_migration/backfill_imported_issue_search_data.rb.
• • Introduced in !90378 (merged) 1 year ago.
• lib/gitlab/background_migration/migrate_links_for_vulnerability_findings.rb.
• • Introduced in !111454 (merged) 9 months ago.
• lib/gitlab/background_migration/populate_vulnerability_dismissal_fields.rb.
• • Introduced in !117478 (merged) 7 months ago.
• lib/gitlab/background_migration/reset_status_on_container_repositories.rb.
• • Introduced in !104858 (merged) 11 months ago.
• lib/gitlab/background_migration/migrate_remediations_for_vulnerability_findings.rb.
• • Introduced in !109397 (merged) 9 months ago.

Desired outcome

For each BBM class in the list:

• Check if the migration can safely be changed
• Fix BackgroundMigration/AvoidSilentRescueExceptions in each BBM class

Related to !136608 (merged)