MC (ParamMC, McMASA): LFE channel is not low pass filtered before encoding

Basic info

• Commit SHA: main
• Platform: all

Bug description

In the MC path, both ParamMC and McMASA employ a TD downmix to the transport channels in the encoder, including the LFE. If the LFE contains signals above the ecpected LFE band width (as is the case for at least for one of the 7.1.4 selection test items) this signal content then shows up in the decoded waveforms (e.g. in ParamMC 7.1.4 in the center channel). Obvious fix is to apply the TD low pass filter that already exists in the discrete LFE coding always on the LFE channel before encoding.

Ways to reproduce

(Clear steps or refer to a failing automated test, e.g. with a pipeline link)