Verify possibly-retired InfluxDB `_internal` fields: httpd.valuesWrittenOK, write.pointsWrittenOK/subWriteDrop/valuesWrittenOK, hh_database

[jstirnaman]

Follow-up to #7557.

Relevant URLs

• content/shared/influxdb-v1/administration/monitor/measurements-internal.md

What

content/shared/influxdb-v1/administration/monitor/measurements-internal.md
documents four _internal fields and one Enterprise-only measurement that
are absent on two live InfluxDB v1.12.4 instances (OSS and Enterprise),
tested after fresh write and query activity:

• httpd.valuesWrittenOK
• write.pointsWrittenOK
• write.subWriteDrop
• write.valuesWrittenOK
• hh_database (measurement)

The four fields are still documented by the Telegraf influxdb input
plugin README (content/telegraf/v1/input-plugins/influxdb.md), so they
may exist only in older InfluxDB 1.x releases rather than being incorrect.
hh_database requires an active hinted handoff failure between cluster
nodes to reproduce, which wasn't testable with the available single-node
Enterprise setup.

A <!-- VERIFY (live instance) --> comment marks the spot in the doc.

Ask

• Confirm whether the four fields exist in any currently supported
  InfluxDB 1.x release, and if so, which version(s).
• Confirm whether hh_database is still emitted by InfluxDB Enterprise
  during hinted handoff, and under what conditions.

Definition of done

• Fields/measurement confirmed to exist (with version) → uncomment and
  document properly, noting the version floor
• Fields/measurement confirmed removed/never existed → delete from the
  doc and drop this note

[davidby-influx]

httpd.valuesWrittenOK exists in the code but is never used. It's use was removed in 1.9.0 by commit 117341fb0f

[davidby-influx]

subWriteDrop was removed for 1.10.0 by commit 85abb3af36 (which was then reverted and unreverted)

[davidby-influx]

write.pointsWrittenOK does not exist and never has.

httpd.pointsWrittenOK would be the closest analog

[davidby-influx]

write.valuesWrittenOK never existed