Add more merging and overriding tests

[amisevsk]

What does this PR do?

Adds a few tests for the merging/overriding package:

• Adds test to cover issue override checkkeys should not assume there is a matching key in the override patch #276 (implemented before I realized the issue had been fixed -- see also: [Overriding] panic when attempting to use Plugin overrides #296)
  • Test fails on commit fb248c2; succeeds on a682303
• Add tests to cover [Merging] passing in nil in MergeDevWorkspaceTemplateSpec causes panic #295 and verify they fail
• Add fix for [Merging] passing in nil in MergeDevWorkspaceTemplateSpec causes panic #295 by adding nil checks to MergeDevWorkspaceTemplateSpec

What issues does this PR fix or reference?

Fixes #295 and provides a regression test for #276

Is your PR tested? Consider putting some instruction how to test your changes

go test ./pkg/utils/...

Docs PR

Bugfix; no docs required.

[davidfestal]

Thanks !

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: amisevsk, davidfestal
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[openshift-ci-robot]

New changes are detected. LGTM label has been removed.