Add regression tests for Int64 array bounds check bypass

[EricGrange]

Summary

This PR adds two regression test cases that verify proper bounds checking for array access with Int64 indices that exceed 32-bit range.

Key Changes

• array_bounds_int64_static.pas: Red test for static array bounds-check bypass where indices with values >= 2^32 incorrectly truncate to their low 32 bits, bypassing range validation
• array_bounds_int64_dynamic.pas: Red test for dynamic array bounds-check bypass through non-variable base expressions with Int64 indices
• array_bounds_int64_static.txt and array_bounds_int64_dynamic.txt: Expected output files showing that out-of-bounds exceptions should be raised for all out-of-range indices

Notable Details

These tests expose a critical security issue in array indexing:

• TStaticArrayExpr.GetIndex() evaluates indices as Int64 but truncates to 32-bit Integer before bounds checking, allowing indices like 2^32 to silently access wrong array elements
• TDynamicArrayExpr evaluation methods similarly declare indices as 32-bit Integer despite receiving Int64 values, bypassing bounds validation for high-value indices
• The tests verify both read and write operations should raise exceptions for out-of-bounds Int64 indices

https://claude.ai/code/session_013gnFMXw8LzjgJz5eHcyYW6