fix: support open generic transitive auto-mocks

[thomhurst]

Summary

• normalize generic single-interface mock discovery to open generic definitions
• emit generic impl, wrapper, member, bridge, factory, and static extension code
• add runtime open-generic factory resolution plus behavioral regression tests for TUnit.Mocks fails for generic interface inheriting IEnumerable<T> in transitive mock generation #5567

Testing

• dotnet test .\TUnit.Mocks.SourceGenerator.Tests\TUnit.Mocks.SourceGenerator.Tests.csproj
• dotnet test .\TUnit.Mocks.Tests\TUnit.Mocks.Tests.csproj

Closes #5567

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[codacy-production]

Not up to standards ⛔

🔴 Issues 4 medium · 26 minor

Alerts:
⚠ 30 issues (≤ 0 issues of at least minor severity)

Results:
30 new issues

Category	Results
UnusedCode	1 minor
BestPractice	2 medium 1 minor
CodeStyle	24 minor
Performance	2 medium

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🟢 Metrics 292 complexity

Metric	Results
Complexity	292

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[azure-pipelines]

Azure Pipelines:
1 pipeline(s) were filtered out due to trigger conditions.

[azure-pipelines]

Azure Pipelines:
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