refactor: eliminate duplicated code in source generators

[vbreuss]

This PR refactors source generator code to eliminate duplication by extracting common XML documentation generation patterns into reusable helper methods. The changes consolidate repetitive string-building logic for generic type parameters and XML documentation tags.

Key changes:

• Introduced helper methods (GetGenericTypeParameters, GetOutGenericTypeParameters, AppendXmlSummary, AppendXmlRemarks, GetTypeParametersDescription, AppendTypeParamDocs, GetAdditionalInterfacesDescription) to replace duplicated code patterns
• Replaced inline XML documentation generation with calls to these helper methods across multiple source generator files
• Changed EscapeForXmlDoc visibility from internal to private as it's no longer needed outside its containing class

[Copilot]

Pull request overview

This PR refactors source generator code to eliminate duplication by extracting common XML documentation generation patterns into reusable helper methods. The changes consolidate repetitive string-building logic for generic type parameters and XML documentation tags.

Key changes:

• Introduced helper methods (GetGenericTypeParameters, GetOutGenericTypeParameters, AppendXmlSummary, AppendXmlRemarks, GetTypeParametersDescription, AppendTypeParamDocs, GetAdditionalInterfacesDescription) to replace duplicated code patterns
• Replaced inline XML documentation generation with calls to these helper methods across multiple source generator files
• Changed EscapeForXmlDoc visibility from internal to private as it's no longer needed outside its containing class

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
Sources.cs	Added new helper methods for generating XML documentation and generic type parameters; refactored existing code to use these helpers
Sources.MethodSetups.cs	Replaced duplicated XML documentation code with helper method calls for method setup interfaces and classes
Sources.IndexerSetups.cs	Replaced duplicated XML documentation code with helper method calls for indexer setup interfaces and classes

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
99.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Test Results

    14 files  ±0      14 suites  ±0   4m 34s ⏱️ -28s
 1 656 tests ±0   1 655 ✅ ±0  1 💤 ±0  0 ❌ ±0 
11 081 runs  ±0  11 080 ✅ ±0  1 💤 ±0  0 ❌ ±0 

Results for commit 13421cc. ± Comparison against base commit eda9bc1.

[github-actions]

🚀 Benchmark Results

Details

BenchmarkDotNet v0.15.8, Linux Ubuntu 24.04.3 LTS (Noble Numbat)

AMD EPYC 7763 2.45GHz, 1 CPU, 4 logical and 2 physical cores

.NET SDK 10.0.101

[Host] : .NET 10.0.1 (10.0.1, 10.0.125.57005), X64 RyuJIT x86-64-v3
Job=InProcess  Toolchain=InProcessEmitToolchain  IterationCount=15

LaunchCount=1  WarmupCount=10

Method	Mean	Error	StdDev	Gen0	Gen1	Allocated
Simple_Mockolate	1.490 μs	0.0213 μs	0.0199 μs	0.2232	-	3.66 KB
Simple_Moq	178.624 μs	1.8053 μs	1.6004 μs	0.4883	-	14.55 KB
Simple_NSubstitute	5.864 μs	0.0646 μs	0.0604 μs	0.5569	0.0076	9.14 KB
Simple_FakeItEasy	6.957 μs	0.0763 μs	0.0714 μs	0.5035	-	8.33 KB

[github-actions]

This is addressed in release v0.44.0.