test() distinguishes NA, NaN in vectors

[MichaelChirico]

NB: targeting #7863

1. test(0, data.table(a=NA_real_), data.table(a=NaN)) currently passes. I'll mark that for follow-up since, IINM, it will require a breaking change to all.equal.data.table().
2. froll.Rraw is not currently passing. @jangorecki could you PTAL and see if we should just update the tests or if this is exposing some unintended behavior?

[MichaelChirico]

Testing out the new stacking feature on GitHub. Locally, I'm still using jj to manage chains.

Let's see how it works! Ideally they work fluidly together.

[github-actions]

• HEAD=test-na-nan much slower for as.data.table.array improved in #7019
• HEAD=test-na-nan much slower for transform improved in #5493
• HEAD=test-na-nan much slower for isoweek improved in #7144
• HEAD=test-na-nan faster P<0.001 for memrecycle regression fixed in #5463
  

Generated via commit de87946

Download link for the artifact containing the test results: ↓ atime-results.zip

Task	Duration
R setup and installing dependencies	6 minutes and 40 seconds
Installing different package versions	13 minutes and 4 seconds
Running and plotting the test cases	5 minutes and 33 seconds