Simplify the configuration of ZBClient

[jwulf]

The ZBClient component supports a lot of backward-compatible constructor options, including multiple constructor signatures.

This makes modification and maintenance a challenge. While adding multi-tenancy support to the Zeebe client, this is causing a lot of friction and accidental complexity.

For the 8.5 release, I will simplify the constructor signature to be a Partial<ZBClientConfig>, and then make the configuration hydrator do the following:

Read all environment variables into a config map, then overwrite that map with any explicit configuration passed to the constructor.

This makes the configuration explicit and simple. The zero-conf constructor is default. All configuration from environment variables is applied, then anything that is explicitly passed to a ZBClient constructor overrides it.