In STS unpacker, fix bug in handling of TS_MSB cycles happening at edge of MS + cleanup

- Replace all legacy hard-coded numerical values for the TS_MSB cycle size by a constant derived in StsXyterMessage from the data format
- Remove deprecated special cases in the handling of the TS_MSB messages which are not present anymore in the current CRI data format
- Do not update TS_MSB and TS_MSB cycle from the MS header when the cycle happened exactly at the end of last MS
- Recompute the TS+MSB in TS offset from the MS heder only when changing the Cycle or the TS_MSB from the same header
- Add static method to convert Message Type into human readable string
- Slight improve/cleanup of debug printouts and debug levels

Was leading to errors and a crash in mCBM 2021 run 1588 files node8_3_0123 and node8_5_0002