release-8.5: Several docs pages misname Grafana panel/dashboard titles (casing/spelling mismatches)

Error Report

1. What is the URL/path of the document related to this issue?

Same issue as #23818, but for the release-8.5 branch specifically:

• https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file (tikv-configuration-file.md)
• https://docs.pingcap.com/tidb/v8.5/troubleshoot-high-cpu-usage (troubleshoot-cpu-issues.md)
• https://docs.pingcap.com/tidb/v8.5/alert-rules (alert-rules.md)
• https://docs.pingcap.com/tidb/v8.5/best-practices/massive-regions-best-practices (best-practices/massive-regions-best-practices.md)
• https://docs.pingcap.com/tidb/v8.5/grafana-performance-overview-dashboard (grafana-performance-overview-dashboard.md)

2. How would you like to improve it?

Confirmed the same 5 panel/dashboard-name mismatches described in #23818 are also present on the release-8.5 branch:

• The TiKV monitoring dashboard's real title is TiKV-Details (hyphenated, both words capitalized — confirmed via the dashboard JSON's own title field in pingcap/monitoring, e.g. Test-Cluster-TiKV-Details). On release-8.5:
  • tikv-configuration-file.md (max-background-gc config item): "TiKV Details" (space instead of hyphen)
  • troubleshoot-cpu-issues.md: "TiKV-details" (lowercase "d"), 2 occurrences
• best-practices/massive-regions-best-practices.md says the panel is "Thread-CPU" (hyphenated), but the real panel title in tikv_details.json is "Thread CPU" (space, no hyphen).
• alert-rules.md (the section starting "For versions earlier than v3.0...") says "Raft propose" (lowercase "propose"), but the real panel title in tikv_details.json is "Raft Propose" (capitalized). A sibling section earlier in the same file already correctly says "Raft Propose".
• grafana-performance-overview-dashboard.md lists a panel bullet as "Execution Duration", but the real panel title in performance_overview.json is "Execute Duration" — matching the section's own heading ("Parse Duration, Compile Duration, and Execute Duration") just above it.

Please apply the same fix to release-8.5 as whatever fix lands for #23818 on master, since these files have diverged content between the branches (e.g. troubleshoot-cpu-issues.md has more instances of the TiKV-details typo on master than on release-8.5).

(Found while reviewing the Japanese translation of these pages on the i18n-ja-release-8.5 branch — the JA translations have already been corrected to match the real panel names, ahead of this EN fix.)

Review the five listed Markdown files on the release-8.5 branch and compare their panel and dashboard names with the titles in the referenced monitoring JSON files. Correct the casing, spelling, hyphenation, and wording mismatches, applying the same fix as #23818 on master. Done means all five pages use the confirmed Grafana titles consistently.