openexr: Specify modules when finding OpenEXR.

openexr: Specify modules when finding OpenEXR.

Specify modules to look for OpenEXR when CMake is used, as we may have
CMake config files instead of pkg-config files that result from building
OpenEXR, which may be built with CMake which is typically the case on Visual
Studio builds.

In this case, Meson does seem to find the 'OpenEXR' package with CMake
after trying pkg-config, but does not consider it enough without the
'modules:' argument.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2014>