Add nats2.14 support.

[s3rius]

Updated async-nats to support new features introduced in 2.14.

[codecov]

Codecov Report

❌ Patch coverage is 70.14925% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.72%. Comparing base (3edcfd6) to head (30f85cb).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/js/stream.rs	70.14%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #54      +/-   ##
==========================================
- Coverage   87.12%   86.72%   -0.40%     
==========================================
  Files          32       32              
  Lines        3122     3141      +19     
==========================================
+ Hits         2720     2724       +4     
- Misses        402      417      +15     

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