Migrate remote tests from PHPUnit to Mocha/Chai

[dstillman]

So this one may be rather tedious, but we really want to stop using PHPUnit for the remote dataserver tests and start using JS and Mocha/Chai like we do everywhere else. And since these are remote integration tests that don't actually need to use the dataserver PHP code, there shouldn't be anything preventing us from doing so, other than a lot of existing tests and support code.

I actually started to look into using GPT to convert the tests, and I think we probably can to some extent, but as a first step we should get the bootstrap/setup code running under Mocha (also perhaps with some help from ChatGPT) with a basic test passing, and then we can iterate from there.