Treat zero MaxNotificationsPerPublish as unlimited (OPC 10000-4)

[romanett]

Proposed changes

Backport commit a5dd6ea (#4047) to master378.

OPC UA defines zero as no notification limit. The message builder compared the queued count directly with zero, so an effective zero limit emitted no event or data-change notifications and left the queues pending. Separately, the revision logic treated a configured Server maximum of zero as a numeric cap, revising a non-zero Client request to zero and silently removing the Client's requested limit.

Fix

• Treat an effective zero limit as unlimited while draining event and data-change queues.
• When the Client requests zero, use the Server's configured maximum, which may itself remain zero/unlimited.
• When the Server maximum is zero, preserve a non-zero Client request, including uint.MaxValue.
• When the Server maximum is finite, cap zero, uint.MaxValue, and larger finite Client requests to that maximum.
• Cover the same revision matrix through both CreateSubscription and ModifySubscription.

Related Issues

• Backport of Treat zero MaxNotificationsPerPublish as unlimited (OPC 10000-4) #4047 (commit a5dd6eae7cc1ab074d62d723194285952560555f)

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.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.26%. Comparing base (db256c6) to head (298ef09).

Additional details and impacted files

@@              Coverage Diff              @@
##           master378    #4263      +/-   ##
=============================================
+ Coverage      60.19%   60.26%   +0.06%     
=============================================
  Files            378      378              
  Lines          79067    79072       +5     
  Branches       13838    13840       +2     
=============================================
+ Hits           47598    47652      +54     
+ Misses         27047    27003      -44     
+ Partials        4422     4417       -5     

Files with missing lines	Coverage Δ
...braries/Opc.Ua.Server/Subscription/Subscription.cs	73.96% <100.00%> (+1.02%)	⬆️
.../Opc.Ua.Server/Subscription/SubscriptionManager.cs	76.79% <100.00%> (+0.45%)	⬆️

... and 8 files with indirect coverage changes

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