tidb_stats_cache_mem_quota can't control stats cache cost

[lilinghai]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

million tables and dml on the tables
set tidb_stats_cache_mem_quota 2gb

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

Release Version: v8.5.0-alpha-279-g9812d85d0d
Edition: Community
Git Commit Hash: 9812d85
Git Branch: HEAD
UTC Build Time: 2024-12-03 17:04:33
GoVersion: go1.23.3
Race Enabled: false
Check Table Before Drop: false
Store: unistore

[hawkingrei]

It is not a bugix. it is implemented by #58052