Get other.Rraw running again in r-devel

[MichaelChirico]

A few changes here:

• We need to mess with the attach order. Originally tried attach.required=FALSE but that's not present on R 3.5.0.
• {ggplot2} internals have moved around again. I think the intent of those tests is just to ensure print(<ggplot-obj>) works without error, so switched those to use the new check_value=FALSE.
• Robustness improvement for a {bit64} test when lacking proper long double. I'm of half a mind to just delete that test because it's only testing {bit64} functionality anyway...
• Since RFC: fail test.data.table() if non-test code produces warnings #7210, warning() outside of test() is caught, so change an intentional warning on Windows to cat().

Split off from #7832 as the actual debugging of package code should be done artisinally.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.01%. Comparing base (dcaa87c) to head (dbaea75).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7833   +/-   ##
=======================================
  Coverage   99.01%   99.01%           
=======================================
  Files          88       88           
  Lines       17286    17286           
=======================================
  Hits        17116    17116           
  Misses        170      170           

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[github-actions]

• HEAD=other-attach-order much slower for transform improved in #5493
  

Generated via commit 4db2f8f

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

Task	Duration
R setup and installing dependencies	2 minutes and 47 seconds
Installing different package versions	1 minutes and 9 seconds
Running and plotting the test cases	5 minutes and 34 seconds

[ben-schwen]

LGTM