Migrate legacy reference test to node test runner

[sammacbeth]

Description:

• After migrating to ESBuild, we were left with some tests that still needed browserify to build, primarily because they use jsdom.
• We should ideally run these tests in node, as running jsdom in the browser (the normal unit-test environment) is a hack.
• This PR moves those remaining reference-tests to a new unit-test environment, that bundles the tests with ESBuild, but targeting node, and runs them with jasmine.
• As the test framework is the same (jasmine), these tests can be written in the same way as the normal unit-tests. The run context (node vs browser) depends on which folder they are in under the unit-tests dir: unit-test/node -> run in node, other folders are run in the browser.
• We might want to migrate other tests to the node runner at some point, as it's much faster.

Requires duckduckgo/content-scope-scripts#643 and duckduckgo/privacy-reference-tests#104 for tests to pass.