Improve performance, and memory pressure of reactive.array

[NullVoxPopuli]

@runspired has this performant version of TrackedArray, that should probably be the default: https://github.com/emberjs/data/blob/main/packages/store/src/-private/record-arrays/identifier-array.ts

Also, and maybe this is more the issue, is that we need to set up some benchmarks to keep in artifacts, so that on each PR, we can run "the benchmark", compare against what's on main, and ensure that things don't regress.

Would be good to set up after this lands: #86

And assigning myself, too -- j/k, can't 😅

[wycats]

@NullVoxPopuli We need to wait until we have prod mode to properly compare the two versions. But I'll take a look at the @runspired version and see if there's anything I can pull in in the meantime.