Backport several OpenEXRCore security fixes
- Fixes CVE-2026-34378 / GHSA-v76p-4qvv-vh4g; closes RHBZ#2455493
- Fixes CVE-2026-34380 / GHSA-q3v8-hw4m-59w5; closes RHBZ#2455534
- Fixes CVE-2026-34588 / GHSA-588r-cr5c-w6hf; closes RHBZ#2455505
- Fixes CVE-2026-34589 / GHSA-p8xc-w3q4-h64x; closes RHBZ#2455501
- Fixes CVE-2026-34379 / GHSA-w88v-vqhq-5p24; closes RHBZ#2455497