feat(jdk-codemodel): resolve Symbol.LocalVariable to its declaring LocalVariableDeclaration

[deer]

Extends Symbol.LocalVariable with an Optional<LocalVariableDeclaration> that links a local variable identifier back to the statement that declared it, mirroring how Symbol.Field and Symbol.Parameter already resolve to their descriptors.

JdkStatementConverter now calls a new registerLocalVariableDeclaration method on JdkExpressionConverter whenever it converts a VariableTree into a LocalVariableDeclaration, populating a map keyed by the resolved javac Element. When JdkExpressionConverter.resolveSymbol later encounters an IdentifierTree whose element kind is LOCAL_VARIABLE, it looks up that map to attach the declaring LocalVariableDeclaration, correctly handling shadowed variables of the same name in nested blocks since resolution is keyed by the distinct javac Element, not by name.