ChannelToken: Dispose HMAC and improve lifetime calculations.

[mregen]

Proposed changes

Issues addressed:

• Channels are not disposed (client and server)
• During long running tests an HMAC object leak was observed.
• The HMAC and SymmetricSign objects were not disposed after use, leading to a small incremental memory leak per key renewal.
• The channel token lifetime is calculated by the system clock, which can change. Instead use the continous HiResClock.TickCount to calculate the lifetimes.
• Token renewal and connection requests are not removed from the request dictionary

Improvements:

• Make ChannelToken disposable. Dispose channels.
• Dispose HMAC and SymmetricSign objects after use.
• Use TickCount to calculate key renewal and key expiry.
• Introduce a 5% jitter to the token renewal timer, to avoid token renewal storms.
• Reduce the allocation per use of the HMAC objects by using ReadOnlySpan and avoid MemoryStream.

Types of changes

What types of changes does your code introduce? Put an x in the boxes that apply. You can also fill these out after creating the PR.

• [x] Bugfix (non-breaking change which fixes an issue)
• [x] Enhancement (non-breaking change which adds functionality)
• [ ] Test enhancement (non-breaking change to increase test coverage)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected, requires version increase of Nuget packages)
• [ ] Documentation Update (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• [x] I have read the CONTRIBUTING doc.
• [x] I have signed the CLA.
• [ ] I ran tests locally with my changes, all passed.
• [ ] I fixed all failing tests in the CI pipelines.
• [ ] I fixed all introduced issues with CodeQL and LGTM.
• [ ] I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• [ ] I have added necessary documentation (if appropriate).
• [ ] Any dependent changes have been merged and published in downstream modules.

Further comments

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 71.10092% with 63 lines in your changes missing coverage. Please review.

Project coverage is 54.93%. Comparing base (56dd06d) to head (3830a43). Report is 1 commits behind head on develop/main374.

Files with missing lines	Patch %	Lines
...c.Ua.Core/Stack/Tcp/UaSCBinaryChannel.Symmetric.cs	72.72%	25 Missing and 5 partials :warning:
...k/Opc.Ua.Core/Stack/Tcp/UaSCBinaryClientChannel.cs	51.06%	21 Missing and 2 partials :warning:
Stack/Opc.Ua.Core/Types/Utils/Utils.cs	22.22%	6 Missing and 1 partial :warning:
Stack/Opc.Ua.Core/Stack/Tcp/ChannelToken.cs	94.73%	1 Missing :warning:
Stack/Opc.Ua.Core/Stack/Tcp/TcpServerChannel.cs	90.00%	1 Missing :warning:
...tack/Opc.Ua.Core/Stack/Tcp/TcpTransportListener.cs	90.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop/main374 #2846 +/- ## =================================================== - Coverage 57.28% 54.93% -2.36% =================================================== Files 352 349 -3 Lines 75539 66129 -9410 Branches 15990 13576 -2414 =================================================== - Hits 43273 36328 -6945 + Misses 27843 25843 -2000 + Partials 4423 3958 -465 ```

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[mregen]

@romanett found more issues, thanks for testing.