database_observability: improve mysql schema collection compatibility

[cristiangreco]

PR Description

Which issue(s) this PR fixes

Notes to the Reviewer

PR Checklist

• CHANGELOG.md updated
• Documentation added
• Tests updated
• Config converters updated

[rgeyer]

I wasn't able to test in depth, but I did try with a MySQL 5.7 docker instance, with the employees schema loaded (not the playground repo, I had other issues with that).

Looks like there are other issues which might be failing before the query that is changed in this PR? 🤔

With MySQL 5.7 and the latest mainline alloy container, these are the associated log lines.

ts=2025-10-23T21:52:56.167615349Z level=error msg="collector error" component_path=/ component_id=database_observability.mysql.mysql_dbo11y collector=query_details err="failed to fetch summary table samples: Error 1054 (42S22): Unknown column 'query_sample_text' in 'field list'"
ts=2025-10-23T21:52:56.171026831Z level=error msg="failed to scan tables" component_path=/ component_id=database_observability.mysql.mysql_dbo11y collector=schema_details err="sql: Scan error on column index 2, name \"CREATE_TIME\": unsupported Scan, storing driver.Value type <nil> into type *time.Time"
ts=2025-10-23T21:52:56.171069041Z level=info msg="no tables detected from information_schema.tables" component_path=/ component_id=database_observability.mysql.mysql_dbo11y collector=schema_details

With MySQL 5.7 and a local binary built with this branch, these are the associated log lines.

ts=2025-10-23T21:59:07.752389418Z level=error msg="collector error" component_path=/ component_id=database_observability.mysql.mysql_dbo11y collector=query_details err="failed to fetch summary table samples: Error 1054 (42S22): Unknown column 'query_sample_text' in 'field list'"
ts=2025-10-23T21:59:07.756370931Z level=info msg="WAL checkpoint loaded" component_path=/ component_id=prometheus.remote_write.metrics_service subcomponent=wal
ts=2025-10-23T21:59:07.756827194Z level=error msg="failed to scan tables" component_path=/ component_id=database_observability.mysql.mysql_dbo11y collector=schema_details err="sql: Scan error on column index 2, name \"CREATE_TIME\": unsupported Scan, storing driver.Value type <nil> into type *time.Time"
ts=2025-10-23T21:59:07.756868177Z level=info msg="no tables detected from information_schema.tables" component_path=/ component_id=database_observability.mysql.mysql_dbo11y collector=schema_details