[3.0] contrib: ffmpeg: update to 4.4.5 / don't rely on MAX_PATH for Windows DLL loading

It also fixes building with newer UWP toolchains.

Only a small part of the first patch is backported.

changed milestone to %3.0.x maintenance

added Component::Build system: Contribs Component::Decoders labels

added MRStatus::Reviewable label

Duplicate of !6268 (merged) which is already merged

closed