[MilCodeGen] Optimize generated ValueSerializers code style and usings

[h3xds1nz]

Description

Resolves numerous IDE warnings and reflects more closely current code-style in derived ValueSerializers.

Also removes redundant usings. Instead of using the collection from the resource tree, we only really need the managed namespace for the resource itself and System.Windows.Markup for ValueSerializer, this is static dependency so the definition doesn't need to be in the resource model itself (same thing as System.Windows.Markup.TypeConverterHelper is directly linked in generator code).

Reviewing ManagedStruct.cs shall be enough to get the grip of the changes, also the changes are always consistent per-folder so 1 file gives you overview of full set of changes for that particular set of resources.

Customer Impact

Cleaner codebase for developers.

Regression

No.

Testing

Local build.

Risk

Low.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull Request Overview

This PR optimizes the generated ValueSerializers code style by simplifying conditional logic and removing redundant using statements.

• Consolidates usings by removing the dynamic iteration over namespaces in favor of static references.
• Streamlines conversion logic with inline ternary operators and pattern matching.

Comments suppressed due to low confidence (1)

src/Microsoft.DotNet.Wpf/src/WpfGfx/codegen/mcg/generators/ManagedStruct.cs:981

• This line uses '[[lowerName]]' assuming it refers to the pattern-matched instance from a previous check; however, it might accidentally reference the earlier declared string variable. A distinct name for the pattern variable would improve clarity and prevent potential conflicts.

return [[lowerName]].ConvertToString(null, ConverterHelper.InvariantEnglishUS);

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 90 lines in your changes missing coverage. Please review.

Project coverage is 11.26680%. Comparing base (6514196) to head (2468f58).
Report is 3 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #10648         +/-   ##
===================================================
+ Coverage   11.22814%   11.26680%   +0.03866%     
===================================================
  Files           3352        3353          +1     
  Lines         668000      667874        -126     
  Branches       74980       74956         -24     
===================================================
+ Hits           75004       75248        +244     
+ Misses        591745      591371        -374     
- Partials        1251        1255          +4     

Flag	Coverage Δ
Debug	11.26680% <25.00000%> (+0.03866%)	⬆️

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