Related to WT-14646

When precise checkpoints are enabled in WiredTiger, content newer than the stable timestamp (or checkpoint timestamp when a checkpoint is running) cannot be evicted to disk - it needs to be retained in the cache. Currently, when a dirty page with updates newer than the checkpoint timestamp is reconciled, WiredTiger performs update-restore eviction.

This ticket is part of the work to optimise this process by adding a heuristic that avoids evicting pages with updates newer than the checkpoint timestamp as long as there isn't excessive cache pressure. This would prevent unnecessary update-restore eviction operations.

The proposed change will:

1. Add logic to the eviction page selection process to check if a page has updates with timestamps newer than:
   • The checkpoint timestamp (if a checkpoint is running)
   • The stable timestamp (if no checkpoint is running)
2. Skip these pages during normal eviction selection when cache pressure is not critical
3. Add additional statistics