Remove babel-plugin-rewire dependency

What does this MR do?

Remove babel-plugin-rewire dependency

This is a follow-up to removing most no-op default exports. In that MR, the "most" was due to the fact that a couple of files were still participating in Karma tests.

Since it turns out that no Karma tests rely on babel-plugin-rewire, that could be removed, allowing the final two instances of workarounds for it to be removed as well.

Finally, the spyOnDependency helper was removed, since it's unused.

WIP

This is marked WIP, since it depends on !37213 (merged).

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done