SF-3686 Enable SignalR reconnecting with statefulness

[pmachapman]

This PR helps the SignalR server and client to reconnect and resend any missed messages if the connection is interrupted for some reason, such as connectivity issues.

I have also cherrypicked a commit from #3638 that will unsubscribed from notifications, to ensure that the server does not remember messages for clients that no longer require SignalR notifications for a sync or draft.

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This change is 

[codecov]

Codecov Report

❌ Patch coverage is 40.00000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.28%. Comparing base (d46a077) to head (70eb3c6).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/SIL.XForge.Scripture/Startup.cs	0.00%	4 Missing ⚠️
...ntApp/src/app/core/project-notification.service.ts	0.00%	3 Missing ⚠️
.../app/sync/sync-progress/sync-progress.component.ts	75.00%	1 Missing ⚠️
...draft-history-list/draft-history-list.component.ts	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3655      +/-   ##
==========================================
- Coverage   83.29%   83.28%   -0.01%     
==========================================
  Files         611      611              
  Lines       37646    37655       +9     
  Branches     6182     6158      -24     
==========================================
+ Hits        31358    31362       +4     
- Misses       5332     5350      +18     
+ Partials      956      943      -13     

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