Background

Design: WRITING-39975. Epic: SPM-4886.

The server needs an emergency brake before it starts setting blind_remove on cursors. wiredTigerBlindWriteRatio no longer controls deletes because its code was removed in WT-18390.

Change

• Add an on/off server parameter that decides whether the server sets blind_remove at all. When off, every delete works the old way.
• Set at startup, with a runtime toggle if that is easy to add.
• Fix or retire wiredTigerBlindWriteRatio.
• Turning it off must not need a new release.

Acceptance criteria

• The parameter exists, is tested in both states, and is off-able without a release.