L1: resurrect TCH tap feature In this new incarnation of our TCH tap feature, we support DL sniffing in all 3 of FR1, HR1 and EFR, and the new implementation will capture every 20 ms frame where the old one silently skipped a frame (sent nothing) during FACCH stealing. The wire interface on RVTMUX changed slightly, and fc-shell tch record will need to be updated to support the new version. TCH UL play or substitution is supported for FR1 and EFR only; support for HR1 can be added later if needed.