.mp4s cannot be played in default projects in UE5.

In UE4 (using DX11), WmfMedia was able to play .mp4 files by default. However, WmfMedia doesn't support playing .mp4s in DX12, which is what is used in UE5. Electra can handle playing .mp4s in UE5, but it's not a plugin that's enabled by default.

All of the above means that, if someone creates a new project and attempts to play an .mp4 without first enabling Electra, it'll error out and prevent playback.

1. Create a new UE5 project.
2. Create a File Media Source and associate it with an .mp4 file.
3. Create a Media Player and open it.
4. Double-click the File Media Source created in step 2.

Results:

The media player remains black; an error from WmfMedia indicates "Format is not supported in D3D12."

Expected Results:

The .mp4 should begin playing in the media player.