Fix mb_update_arrayptr() false matches after array reallocation

[spatial-dan]

Prevent mb_update_arrayptr() from rebinding a registered array to the wrong allocation when the allocator reuses an address from an earlier reallocation cycle. The mb_update_arrayptr() matched arrays using values retained in regarray_oldptr[]. Those values could outlive their reallocation cycle. If the allocator later reused one of those addresses, a local pointer—such as a sidescan longitude array—could falsely match an earlier bathymetry registration and be rebound to the wrong buffer.

Fix

• Clear saved pointer values at the start of each mb_update_arrays() cycle.
• Prefer the stable registered pointer-variable address when resolving a handle.
• Fall back to the saved pre-reallocation pointer for local copies used by mb_read(), mb_get(), and mb_get_all().
• Clear saved pointer values after successful matches.

Added tests covering:

• simultaneous bathymetry and sidescan growth
• registered-handle matching in the presence of a stale collision
• a deterministic stale-address collision across staged reallocations