Remove blacklist/whitelist language in bulk-insert-safe

What does this MR do?

Remove blacklist/whitelist language in bulk-insert-safe code and docs.

I went for allowed vs unsafe. It's not a dichotomy but that's OK, the important thing is that it's easy to understand, and it sounded better than allowlist or denylist.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Closes #219967 (closed)