[Feature][UI] Ability to reorder tests

[YodaDaCoda]

Sometimes it makes logical sense for certain tests to be grouped next to each other, for example testing a few of ways of doing something in jQuery, versus doing the same thing a few ways in pure JS.

When editing a benchmark to add a new test, the new test is always added at the bottom, but it might be better placed (according to the above logic) next to more similar tests.