Include DTX in ISM conditions in self-test

After Contribution 15 (https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/wikis/Contributions/15-DTX-CNG-for-ISM) was merged into the main, a few self-test conditions are proposed to be added to cover the new functionality, namely:

• // 2 ISM with metadata at 32 kbps, 48 kHz in, 48 kHz out, DTX on, HOA2 out
• // 2 ISM with metadata at 80 kbps, 48 kHz in, 48 kHz out, DTX on, STEREO out
• // 4 ISM with metadata at 48 kbps, 48 kHz in, 48 kHz out, DTX on, BINAURAL ROOM out, DTX on, random FEC at 5%
• // 4 ISm with/without metadata bitrate switching from 24.4 kbps to 256 kbps, 48 kHz in, 48 kHz out, DTX on, HOA3 out