add requires_utf8 argument to tests

[ben-schwen]

Closes #7336
Closes #1343
Closes #7333

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.96%. Comparing base (3e579ee) to head (8d85972).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7388   +/-   ##
=======================================
  Coverage   98.96%   98.96%           
=======================================
  Files          87       87           
  Lines       16737    16741    +4     
=======================================
+ Hits        16563    16567    +4     
  Misses        174      174           

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[github-actions]

• HEAD=tests_requires_utf8 stopped early for isoweek improved in #7144
• HEAD=tests_requires_utf8 slower P<0.001 for DT[by,verbose=TRUE] improved in #6296
• HEAD=tests_requires_utf8 slower P<0.001 for memrecycle regression fixed in #5463
  

Generated via commit 8d85972

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

Task	Duration
R setup and installing dependencies	3 minutes and 1 seconds
Installing different package versions	44 seconds
Running and plotting the test cases	4 minutes and 9 seconds

[aitap]

Sorry if I'm late to note this, but wouldn't a more reliable test for this be the same thing as we currently use for ñ in test 2266? A test may require some symbols (ñ, ü, ん) to be representable in the native encoding. The symbols may be represented using Unicode escapes (\uXXXX) as they currently do. If !identical(foo, enc2native(foo)), then the test must be skipped.

[ben-schwen]

The symbols may be represented using Unicode escapes (\uXXXX) as they currently do. If !identical(foo, enc2native(foo)), then the test must be skipped.

Good point. I have integrated this for the utf8_check.