Fix optional parameter ordering in generated TS/CS clients

[lahma]

This was a regression caused by #5044 . The PR unintentionally "fixed" the swallowed double-OrderBy where only second one would run by changing second one to ThenBy, but actually the second one was the primary ordering.

Now trying to follow the desired path were anything non-optional makes priority in ordering and only after then the parameter's actual position is being considered.

fixes #5131

[Copilot]

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (3)

src/NSwag.CodeGeneration.TypeScript/Models/TypeScriptOperationModel.cs:45

• Verify that reversing the ordering with '!p.IsRequired' correctly prioritizes required parameters as intended, since the test expects required parameters to appear before optional ones.

.OrderBy(p => !p.IsRequired)

src/NSwag.CodeGeneration.CSharp/Models/CSharpOperationModel.cs:61

• Confirm that using '!p.IsRequired' to order required parameters before optional ones aligns with the expected client output in C#.

.OrderBy(p => !p.IsRequired)

src/NSwag.CodeGeneration.CSharp/Models/CSharpOperationModel.cs:62

• Check if the additional ordering based on whether 'p.Default' is null is intentional to further prioritize parameters, and ensure it does not conflict with the desired ordering logic.

.ThenBy(p => p.Default == null)