feat: isolates for compute heavy tasks

[1-leo]

related to #319

[codecov]

Codecov Report

❌ Patch coverage is 82.03125% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.87%. Comparing base (f053c29) to head (f368849).
⚠️ Report is 12 commits behind head on master.

Files with missing lines	Patch %	Lines
...kages/ndk/lib/shared/isolates/isolate_manager.dart	72.41%	16 Missing ⚠️
...s/ndk/lib/domain_layer/usecases/relay_manager.dart	88.57%	4 Missing ⚠️
.../lib/shared/decode_nostr_msg/decode_nostr_msg.dart	90.90%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #327      +/-   ##
==========================================
+ Coverage   70.83%   70.87%   +0.03%     
==========================================
  Files         136      139       +3     
  Lines        5051     5157     +106     
==========================================
+ Hits         3578     3655      +77     
- Misses       1473     1502      +29     

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[1-leo]

• nip01 refactor
• check if nip01 refactor is compatible with https://github.com/nostrlabs-io/zap-stream-flutter

[frnandu]

don't forget to also replace Nip46EventSigner jsonDecode usage with isolate

[frnandu]

libs to maybe try if it makes sense for our pool management requirements:

• https://pub.dev/packages/isolate_manager
• https://pub.dev/packages/worker_manager