Conditionally foward the std crate feature for string-interner

[Robbepop]

This no longer enables string-interner usage when enabling std crate feature without also enabling hash-collections.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.58%. Comparing base (1aa2256) to head (5549b26).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1304   +/-   ##
=======================================
  Coverage   81.58%   81.58%           
=======================================
  Files         306      306           
  Lines       25270    25270           
=======================================
  Hits        20616    20616           
  Misses       4654     4654           

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