The metric of InfoSchema V2 Cache Size needs contain tidb instance name

[lilinghai]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

It is better change used to tc-tidb-0-used

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-303-gcdfdb8a90e
Edition: Community
Git Commit Hash: cdfdb8a
Git Branch: HEAD
UTC Build Time: 2024-12-09 10:26:11
GoVersion: go1.23.4
Race Enabled: false
Check Table Before Drop: false
Store: unistore

[jebter]

Releted to issue: #50959