[backport] contrib: vpx: update to 1.15.2

contrib: vpx: update to 1.15.2

This release fixes CVE-2025-5283 (bug webm:413411335), and is ABI compatible
with the previous release.

(cherry picked from commit 5869fc3ef1f33649cd5606117f9692e73a2ea4e4)

contrib: vpx: update to 1.15.1

The dropped patches have been merged upstream.

(cherry picked from commit 6351a747182cdfee5c2a7341083b6196254a160b)