Add OnTokenActivated event for token change notifications

[marcschier]

Proposed changes

Add a new event OnTokenActivated to the ITransportChannel class to notify when a channel token is activated. Implemented this event in the HttpsTransportChannel class within the Opc.Ua.Bindings namespace. Introduced a protected internal OnTokenActivated event handler in the UaSCBinaryChannel.Symmetric class, invoked during token changes in the ActivateToken and DiscardTokens methods.

Related Issues

• Fixes #

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[codecov]

Codecov Report

Attention: Patch coverage is 45.45455% with 6 lines in your changes missing coverage. Please review.

Project coverage is 55.31%. Comparing base (ce33d63) to head (2b376ce).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
Stack/Opc.Ua.Core/Stack/Client/UaChannelBase.cs	0.00%	2 Missing ⚠️
...k/Opc.Ua.Core/Stack/Https/HttpsTransportChannel.cs	0.00%	2 Missing ⚠️
...pc.Ua.Core/Stack/Tcp/UaSCBinaryTransportChannel.cs	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2868      +/-   ##
==========================================
- Coverage   55.70%   55.31%   -0.39%     
==========================================
  Files         352      352              
  Lines       67332    67343      +11     
  Branches    13806    13808       +2     
==========================================
- Hits        37506    37253     -253     
- Misses      25792    26006     +214     
- Partials     4034     4084      +50     

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[mregen]

please reopen against develop/main374