oracledb_cdc: Add new time to first row metric to visualise SQL timings

[josephwoodward]

This change:

• Adds a new oracledb_cdc_logminer_time_to_first_row_ns metric that helps visualise how long LogMiner takes querying relevant change data.
•  Clean up leaked context go routine upon reconnect

[claude]

Commits

1. oracledb_cdc: Fix leaking Go routine on streaming reconnect loop — the message portion must start lowercase ("Fix" → "fix"). Otherwise format and granularity are good (leak fix and new metric are correctly split into separate commits).

Review
Small, focused change: fixes a leaked context goroutine in the streaming reconnect loop by capturing and deferring cancel() on the SoftStopCtx, and adds an oracledb_cdc_logminer_time_to_first_row_ns timer metric. The defer cancel() is correctly scoped inside the worker goroutine, and the time-to-first-row timing logic is correct.

LGTM

[claude]

Commits

1. Commit oracledb_cdc: Fix leaking Go routine on streaming reconnect loop — the message portion must start lowercase and use imperative mood, so this should be fix leaking ... rather than Fix leaking .... The second commit (add time to first row metric) is compliant.

Review
Small, focused change: fixes a leaked context cancel func in the streaming goroutine and adds a time_to_first_row LogMiner metric. Both changes are correct — defer cancel() is scoped to the goroutine, and the firstRow guard records the timing exactly once per query.

LGTM