Use private_sndStamp as the InfluxDB timestamp

The definition of which timestamp is used as the InfluxDB time is done in the connector configuration. The default behavior is to use sys_time(). We want to replace that by private_sndStamp obtained from the SAL topics.

In DM-21391, we implemented the --timestamp option in the Kafka connect manager to configure the connector:

https://kafka-connect-manager.lsst.io/cli-reference.html#cmdoption-connect-manager-create-influxdb-sink-timestamp

and in this PR we changed the connector to support to Unix timestamps as double
https://github.com/lensesio/stream-reactor/pull/626

That was released in the version 1.2.3 of the connector:

https://github.com/lensesio/stream-reactor/releases/tag/1.2.3

but, unfortunately, that version introduced a regression and cannot be used (DM-21895).

In this ticket, we'll build a special version of the connector previous to 1.23 that supports Unix timestamps as double.

We'll also need to update the kafka connect manager Helm chart so that we can configure which timestamp to use.

Then, we'll deploy the new connector in the Tucson teststand. For testing the connector with the private_sndStamp we'll send data to a second database.