Currently, in test_util.h, the precise_checkpoint flag is hardcoded to true when running in disagg configuration.

While it is mandatory for disagg to use precise checkpoints, this should not be enforced through hardcoding. Instead, precise_checkpoint should remain a configurable option:

• It should be possible to manipulate it via test/format and test/checkpoint configurations.
• If precise_checkpoint is not enabled for disagg, the tests should fail explicitly rather than silently overriding the setting.

Acceptance Criteria:

1. Remove the hardcoded precise_checkpoint = true in test_util.h.
2. Expose precise_checkpoint as a proper configuration option in test/format and test/checkpoint
3. Add validation so that in disagg mode, tests fail if precise_checkpoint is not explicitly enabled.
4. Update affected test/format and test/checkpoint configs accordingly.