Don't unnecessarily restrict create_element to borrowed names

[2xsaiko]

This allows passing owned strings to create_element by making the bounds for the name the same as in the parameter for BytesStart::new.

[Mingun]

Please add a changelog entry. Do not forget to add actual link in section with links, contributors frequently forget about that. Please keep the links list sorted by issue number.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.24%. Comparing base (5d76174) to head (79d5d4c).
Report is 3 commits behind head on master.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #722   +/-   ##
=======================================
  Coverage   61.24%   61.24%           
=======================================
  Files          39       39           
  Lines       16277    16277           
=======================================
  Hits         9969     9969           
  Misses       6308     6308           

Flag	Coverage Δ
unittests	61.24% <100.00%> (ø)

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