Untrack kvproto generated files; align evaluation/ with qiazh

- Remove ThirdParty/kvproto/generated/* from tracking (kept locally,
  regenerated via ThirdParty/kvproto/generate_cpp.sh). Add to .gitignore.
- Restore evaluation/2026-04-23/* to qiazh's pre-merge-tikv-bugfix versions.
- Drop zhangt-only evaluation/2026-04-20-merge/ and evaluation/backend_comparison/.
- Trim evaluation/distributed/ to only the Insert dominant benchmark essentials
  (README.md, run_distributed.sh, configs/benchmark_insert_dominant_template.ini).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: TerrenceZhangX

.gitignore

@@ -472,3 +472,4 @@ benchmark_logs/
 output_*.json
 cluster.conf
 cluster_1node.conf
+ThirdParty/kvproto/generated/