MFH: r530724 r530737 r530860

multimedia/obs-studio: Install one more .cmake file to support some use cases

multimedia/obs-studio: Install ObsPluginHelpers.cmake to facilitate plugins

multimedia/obs-studio: Update 25.0.3 -> 25.0.4

Chengelog: https://github.com/obsproject/obs-studio/releases/tag/25.0.4

This is mostly a bugfix release, therefore requesting MFH.

Approved by: ports-secteam (joneum)