core: use ::operator delete for RVec heavy storage on Windows

[wacfrr]

This Pull request:

Fixes a cross-module/cross-CRT heap allocation mismatch in RVec on Windows platforms. This issue can lead to undefined behaviors, memory corruption, or silent exits when memory allocated inside RVec is freed across module boundaries (e.g., between a pre-compiled DLL and JIT-generated code).

Changes or fixes:

• math/vecops/src/RVec.cxx: In SmallVectorBase::grow_pod, replaced malloc/realloc/free with ::operator new(std::nothrow) and ::operator delete, guarded by #ifdef _WIN32.

• math/vecops/inc/ROOT/RVec.hxx: In SmallVectorTemplateBase::grow and destructor-related deallocations, applied the same guarded replacement to ensure all heap operations are unified across the class layout.

These changes are strictly restricted to Windows via platform macros; Linux and macOS targets remain completely untouched to preserve their high-performance native realloc paths.

Checklist:

• tested changes locally
• updated the docs (if necessary)

This PR fixes #22449

[jblomer]

This will need a matching change in the RNTuple treatment of RVecs