Feature/pascal case

[rdeininger]

Changes Summary

1. OCL Function Handling Refactor

• Moved built-in OCL functions (oclIsKindOf, oclIsTypeOf, oclAsType, oclIsUndefined,
  oclIsInvalid) out of the basicExpression rule and into the function rule in the
  ANTLR4 grammar (antlr4/OCL.g4) and the corresponding visitor logic in
  OclToCSharpConverter.cs.

2. Grammar Fix for let/if in Logical Expressions

• Fixed the OCL grammar so that let-in expressions and if-then-else expressions are
  correctly parsed as the right-hand side of logical operators (implies, and, or, xor).
• Previously these caused parse errors or incorrect ASTs in expressions like:
  x implies let y = ... in ...
  x implies if ... then ... else ... endif

3. OCL Grammar Refactor

• Consolidated and cleaned up grammar rules to remove ambiguity and improve
  parse coverage for complex nested expressions.
• Improved test data in testdata/Consolidated_OCLAndCSharp.md and
  testdata/SysML_OCLAndCSharp.md with additional edge-case OCL inputs.

4. PascalCase Property and Method Conversion

• Per C# coding guidelines, all OCL property and method names in the generated
  C# output are now converted to PascalCase.
• Lambda parameter names and let-binding variable names remain camelCase
  (they are local variables, not C# members).

Implementation details (OclToCSharpConverter.cs):

• Added _localVariables HashSet for tracking lambda/let variable scopes.
• Added ToPascalCase(string) helper: uppercases the first character unless the
  name is a local variable or already starts with an uppercase letter.
• Applied ToPascalCase at all identifier emission points:
  • VisitIdentifier
  • VisitExpression (derivation form LHS)
  • VisitBasicExpression (member access, qualified_name segments)
  • BuildDotMethodCall (including keyword-token operations like isUnique)
  • BuildArrowGenericCall, BuildArrowSimpleOrChained
  • BuildOclAsType, BuildArrowOclAsType, BuildSelectByKind, BuildAtAccess
• Local variable scope tracked in: BuildCollectionOp, BuildReject, BuildOne,
  BuildClosure, BuildIsUnique, BuildIterate, VisitLetExpression.
• ApplyImplicitSelf regex patterns updated from [a-z_] to [A-Za-z_] so they
  correctly match PascalCased identifiers.
• Fixed qualified_name handler to strip OCL _'keyword' syntax (e.g. _'in' → In).
• Fixed ->at(expr).member: the optional trailing member access after ->at() was
  previously dropped; it is now included in the output (e.g.
  foo->at(1).bar → foo.ElementAt(0).Bar).

Test data updates:

• testdata/Consolidated_OCLAndCSharp.md: all 35 C# blocks regenerated.
• testdata/SysML_OCLAndCSharp.md: all 611 C# blocks regenerated.
• src/Ocl2CSharp.Tests/OclToCSharpConverterTests.cs: ~100+ hardcoded expected
  values updated to PascalCase.

[philippkalenda]

possible NullRef?

[philippkalenda]

possibly check all other usage of GetChild