PR #88539 - sql: add telemetry for statistics forecast usage

[cockroach-teamcity]

Exalate commented:

Related PR: cockroachdb/cockroach#88539
Commit: cockroachdb/cockroach@ab38868

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Release note (ops change): Add five new fields to the sampled_query
telemetry events:

• ScanCount: Number of scans in the query plan.
• ScanWithStatsCount: Number of scans using statistics (including
  forecasted statistics) in the query plan.
• ScanWithStatsForecastCount: Number of scans using forecasted
  statistics in the query plan.
• TotalScanRowsWithoutForecastsEstimate: Total number of rows read by
  all scans in the query, as estimated by the optimizer without using
  forecasts.
• NanosSinceStatsForecasted: The greatest quantity of nanoseconds that
  have passed since the forecast time (or until the forecast time, if it
  is in the future, in which case it will be negative) for any table
  with forecasted stats scanned by this query.

Jira Issue: DOC-5916