OpenImageIO v2.5.15.0

Release 2.5.15.0 (Sep 1, 2024) -- compared to 2.5.14.0

• ffmpeg: Add proper detection of new FFmpeg versions #4394 (by Darby Johnston)
• ffmpeg: Retrieve timecode metadata #4396 (by Darby Johnston)
• png: Bug in associateAlpha botched alpha=0 pixels #4386
• raw: Expose additional white balancing hints #4360 (by Anton Dukhovnikov)
• oiiotool: -i:ch=... didn't fix up alpha and z channels #4373
• fix: Catch potential OCIO exception that we were missing #4379
• build: Finish removing Imath include #4371 (by Thiago Ize)
• tests: Adjust RB-2.5 simd_test to allow a little more slop on fast_exp #4372