contrib: vpx: update to 1.12.0
Notable changes:
- This release adds optimizations for Loongarch, adds support for vp8 in the real-time rate control library, upgrades GoogleTest to v1.11.0, updates libwebm to libwebm-1.0.0.28-20-g206d268, and includes numerous bug fixes.
Bug fixes:
- Fix to a crash related to {vp8/vp9}_set_roi_map.
- Fix to compiling failure with -Wformat-nonliteral.
- Fix to integer overflow with vp9 with high resolution content.
- Fix to AddNoiseTest failure with ARMv7.
- Fix to libvpx Null-dereference READ in vp8.