Uplift sinon to 19+

[jkuester]

Describe the issue
Sinon 19 changed the way useFakeTimes works so that calling that function ends up automatically mocking a bunch of stuff.

In some of our tests, it does not work to have everything mocked (particularly, I have observed issues when mocking nextTick when using @medic/memdown). One solution is to just limit which functions are mocked.

So, you might have original test code that looks like this:

sinon.useFakeTimers(NOW.valueOf());

To fix it, use the toFake option to include only the actual functions that need to be faked for your test.

sinon.useFakeTimers({ now: NOW.valueOf(), toFake: ['Date']});

FTR, here are the list of all the valid function names I know of:

    const clock = sinon.useFakeTimers({ now: NOW.valueOf(), toFake: [
      'setTimeout', 'clearTimeout', 'setInterval', 'clearInterval', 'setImmediate', 'clearImmediate', 'hrtime', 'Date', 'nextTick'
    ]});