graphics/openexr*: upgrade to 3.3.1

ChangeLog: https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.3.1

Also add a local docs/CMakeLists.txt patch to add an exrmetrics man
page, omission reported upstream to
https://github.com/AcademySoftwareFoundation/openexr/issues/1881