psi: resolve memory corruption segfaults and runtime panics

[wenxuanjun]

This PR fixes critical stability issues including stack-use-after-return segfaults and runtime interface casting panics.

Previously, AST node factory methods (e.g., create_element) returned struct values. When these values were assigned to the PsiElement interface, the interface's internal data pointer often pointed to temporary stack memory. Once the function returned, accessing these interface methods resulted in reading garbage memory, causing random segmentation faults. So modified to allocate them on heap, guaranteeing valid lifecycles for AST nodes.

And in SelectorExpression, unexpected AST node types caused runtime panics when blindly casting to the ReferenceExpressionBase interface (e.g., src.analyzer.psi.PsiElementImpl cannot be cast to ...). So implemented ReferenceExpressionBase interface for Identifier and added a safe fallback wrapper for unknown node types to prevent panics.

Resolves #80, resolves #110, resolves #152, resolves #162.

[spytheman]

Thank you for working on this 🙇🏻 .

It will make v-analyzer a lot more stable and usable.