Enhance defaults.merge function.

[aabouzaid]

What does this PR do?

In defaults.merge function:

• Add merge_lists option.
• Add in_place option.
• Write unit tests.

Previous Behavior

Lists were not merged, and no unit test for merge function.

New Behavior

• Allow to merge lists.
• Allow to keep original dicts untouched and create new dict.
• Unit test.

Tests written?

Yes

Commits signed with GPG?

Not yet

[rallytime]

@aabouzaid Can you fix this lint error? https://jenkins.saltstack.com/job/PR/job/salt-pr-lint-n/17053/violations/file/tests/unit/modules/test_defaults.py/

[aabouzaid]

@rallytime Akh, a typo 🤕
Fixed :-)

[aabouzaid]

I also added an arg to don't copy in place, so it keeps the orig dicts untouched.
The original behavior still the same (in_place=True by default).

[garethgreenaway]

@aabouzaid Looks like there are still a couple more lint errors. Would you mind taking care of those?

[aabouzaid]

@garethgreenaway Fixed :-)

[garethgreenaway]

@aabouzaid Awesome! Thanks! Just waiting for automated tests to finish then we should be good to go.