Fix SIGBUS crash in wechat_qrcode during process shutdown

[0AnshuAditya0]

Fixes opencv/opencv#27971

Problem:
Double-free crash in std::vector<zxing::Refzxing::qrcode::Version>::~vector()
during process shutdown when using wechat_qrcode module. The crash occurred with
error "free(): double free detected in tcache 2" and SIGBUS signal.

Root Cause:
Static member variable VERSIONS was destroyed during shutdown while Ref
objects still held references, causing double-free due to static initialization
order fiasco.

Solution:
Converted static member variable to Meyer's singleton pattern with heap allocation.
The vector is intentionally never destroyed, preventing the double-free during
shutdown. This is a standard pattern for avoiding static destruction order issues.

Changes:

• version.hpp: Changed VERSIONS declaration to getVersions() function
• version.cpp: Implemented getVersions() with function-local static pointer
• version.cpp: Updated all 15+ references to use getVersions() instead of VERSIONS

Testing:

• Existing tests pass without crashes
• No SIGBUS crash on shutdown
• Small intentional memory "leak" (singleton pattern) is acceptable