Read credentials from envs or command line

[sashayakovtseva]

Real-life example: you deploy sinker with k8s/nomad and don't want to store raw credentials in a config file. One option would be to feed entire config file to some secrets storage, another approach is to enrich public config file with credentials from envs in runtime.

In this PR:

• add ability to specify kafka and clickhouse credentials in envs or command line options

Chores:

• use upper case for sql syntax
• override err var in inlined if clause
• inverse if/else logic to get rid of unnecessary else clause
• match project's go version with gh actions

[yuzhichang]

Thank you!