This issue was created based on a discussion about #176.

General guidelines for metric instrumentation units require that for measuring durations, seconds should be used:

• When instruments are measuring durations, seconds (i.e. s) SHOULD be used.

However, the following DB client metrics still use milliseconds for measuring durations:

• db.client.connections.create_time
• db.client.connections.wait_time
• db.client.connections.use_time

For consistency, those histograms should be changed to use seconds. Those metrics are already in use, and to avoid unnecessary disruptions the change should happen during stabilization of DB semantic conventions and should be covered by the OTEL_SEMCONV_STABILITY_OPT_IN mechanism.