Make log crate feature enabled by default

[fzyzcjy]

Changes

Close #2243

Checklist

• An issue to be fixed by this PR is listed above.
• New tests are added to ensure new features are working. Please refer to this page to see how to add a test.
• ./frb_internal precommit --mode slow (or fast) is run (it internal runs code generator, does auto formatting, etc).
• If this PR adds/changes features, documentations (in the ./website folder) are updated.
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.05%. Comparing base (4beab7f) to head (a54c0dd).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2245      +/-   ##
==========================================
- Coverage   99.06%   99.05%   -0.01%     
==========================================
  Files         488      488              
  Lines       20184    20195      +11     
==========================================
+ Hits        19995    20005      +10     
- Misses        189      190       +1     

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[aran]

Is this kind of a breaking change for users who set up their own logging according to the previous instructions?

e.g. prior to this change, users not using the 'log' feature can be calling log::set_logger.
Now that is called automatically, so it gets called twice and errors result.

[fzyzcjy]

@aran Hmm, I do not expect this to be a breaking change, but looks like yes, and I will consider more carefully next time :( But this also looks like a bugfix: the semantics and doc says frb setup logging automatically, so we should do that.