Improve submit_batch_script logging

[cmd-ntrf]

Adds:

• logging of subvars (info)
• logging of self.get_env (debug)

Changes:

• the logging level of the submit script from info to debug.

The rational is that it is easier to parse subvars dictionary in a separate log than the multiline submit script, which would then be only useful in a debug context.

Removes:

• cmd from the Job submitted info log, since it is was already logged before.

This PR also introduces the usage of logging argument instead of concatenating string with +. I will follow with a second PR that standardize logging to use argument instead of string concatenation systematically.

[mbmilligan]

Hi, after we update the test matrix can you make a commit to this to trigger rerunning the CI?

[consideRatio]

This looks reasonable, thank you @cmd-ntrf!