fix: do not print host_base to stdout

[MalinAhlberg]

Related issue(s) and PR(s)
This PR closes #525 .

Description

• Information about host base is now printed to stderr.
• Tests are updated
• The actual printing function is moved to helpers, to simplify the process in case we want to update the message in the future.

How to test
For example, run

$ sda-cli -config testing/s3cmd.conf upload go.sum

And make sure the info about the host base is in stderr.
Also test that counting the number of files works:

sda-cli -config s3cfg list  | wc -l
The provided access token expires in 12 hours and 24 minutes.
Consider renewing the token.
Remote server (host_base): localhost:18000
1

And similarly for download.

[jbygdell]

Two unnecessary blank lines but else fine.

[nanjiangshu]

Looks good!

[MalinAhlberg]

I have applied Jocke's suggestion, rebased on main, and fixed the integration test.

[aaperis]

Works great :-)