Restore other.Rraw tests to working state

[MichaelChirico]

Motivated as a follow-up to #6583, wound up addressing some other things that were plaguing my fix-iterate loop.

Also note the new test does not exactly match the old behavior (i.e. using knitr.Rout.save), which results from R CMD BATCH on the tests/knitr.R file, instead I'm just matching the md output contents with tools::Rdiff().

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.96%. Comparing base (3c06138) to head (e243147).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7560   +/-   ##
=======================================
  Coverage   98.96%   98.96%           
=======================================
  Files          87       87           
  Lines       16737    16737           
=======================================
  Hits        16563    16563           
  Misses        174      174           

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[ben-schwen]

LGTM, TY!