[FEATURE] Add per-database scrape times metric

[wes-pro]

Summary

Currently exporter exposes oracledb_exporter_last_scrape_duration_seconds metric which return total scrape time. This is request to add per-database scrape duration metric, possibly other like scrape errors too.

Motivation

Query times per-database are itself valueable information about database responsibility.

Proposed Solution

Change existing metrics to be labeled by database id or add new metric with per-database resolution.

Alternatives Considered

Additional Context

[anders-swanson]

Thanks for reporting this @wes-pro. I like this feature suggestion and will roll it into the exporter