PMM-15195 Fixes and MySQL 9.7 changes.

[JiriCtvrtka]

PMM-15195

MySQL Exporter PR: percona/mysqld_exporter#387
PT PR: percona/percona-toolkit#1152
FB: Percona-Lab/pmm-submodules#4479

Summary

Adds PMM dashboard compatibility for Oracle MySQL 9.7 while preserving compatibility with older exporters and MySQL versions.

• Updates InnoDB checkpoint, redo, purge, AHI, and neighbor flush panels.
• Uses canonical mysql_innodb_redo_log_* metrics with legacy metric fallbacks.
• Fixes InnoDB Buffer Pool and Compression CPU label joins.
• Removes the fixed one-hour query interval from Compression CPU panels.
• Fixes Performance Schema panels so zero-valued counters remain visible.
• Adds Community MySQL table activity fallback using
  performance_schema.table_io_waits_summary_by_table.
• Adds Query Cache compatibility notices for MySQL 8.0 and newer.
• Fixes compatibility notice sizing and surrounding panel layout.
• Documents the metric source used by Table Details for Oracle MySQL,
  Percona Server, and MariaDB.

Related changes

This PR should be released together with:

• mysqld_exporter MySQL 9.7 metric compatibility changes.
• Percona Toolkit MySQL 9.7 Service Summary changes.

Test plan

• Validated all modified dashboard JSON files.
• Validated PromQL syntax against the PMM metrics API.
• Connected Oracle MySQL 9.7 to a PMM Feature Build.
• Verified mysqld_exporter and QAN agents are running.
• Verified all affected canonical PromQL queries return data.
• Generated InnoDB redo, checkpoint, purge, AHI, neighbor flush,
  compression, and table activity workloads.
• Verified Top Tables by Rows Read/Changed receive data.
• Verified Query Cache remains empty on MySQL 9.7 and displays an
  explanatory compatibility notice.
• Verified Performance Schema zero-valued metrics are displayed.

[JiriCtvrtka]

@copilot review

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 37.04%. Comparing base (31318c7) to head (92bad89).
⚠️ Report is 39 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5648      +/-   ##
==========================================
- Coverage   43.59%   37.04%   -6.56%     
==========================================
  Files         415      215     -200     
  Lines       43134     7157   -35977     
  Branches        0      591     +591     
==========================================
- Hits        18804     2651   -16153     
+ Misses      22454     4311   -18143     
+ Partials     1876      195    -1681     

Flag	Coverage Δ
admin	34.96% <ø> (+0.17%)	⬆️
agent	?
managed	?
unittests	41.29% <ø> (?)
vmproxy	?

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[JiriCtvrtka]

@copilot review

[JiriCtvrtka]

@copilot review

[JiriCtvrtka]

@copilot review