[Client] Set default timout hint based on OperationTimeout of the TransportChannel

[romanett]

Proposed changes

This PR make the ClientBase class set a default Operation Timeout that allows the server to cancel longrunning requests after the Timeout expired.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• 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

• I have read the CONTRIBUTING doc.
• 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

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[Copilot]

Pull Request Overview

This PR adds a default timeout hint mechanism to the ClientBase class by setting the TimeoutHint in request headers based on the OperationTimeout of the transport channel when no explicit timeout is provided.

• Automatically sets TimeoutHint to the OperationTimeout value when it's not explicitly specified (value is 0)
• Enables servers to cancel long-running requests after the timeout period expires
• Improves request management by providing default timeout behavior

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[codecov]

Codecov Report

❌ Patch coverage is 42.85714% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.66%. Comparing base (47b360d) to head (cea2c38).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...ibraries/Opc.Ua.Client/Session/TraceableSession.cs	0.00%	2 Missing ⚠️
Stack/Opc.Ua.Core/Stack/Client/ClientBase.cs	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3178   +/-   ##
=======================================
  Coverage   57.65%   57.66%           
=======================================
  Files         365      365           
  Lines       79412    79419    +7     
  Branches    13862    13865    +3     
=======================================
+ Hits        45788    45798   +10     
- Misses      29370    29373    +3     
+ Partials     4254     4248    -6     

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[romanett]

Better Introduce a separate Property to allow to configure the "DefaultServiceCallTimeoutHint"