PixelRawDataByteStreamCnv: Use AthConstConverter.

Scott Snyderrequested to merge
ssnyder/athena:constcnv.PixelRawDataByteStreamCnv-20201111 into master

Change PixelRawContByteStreamCnv to derive from AthConstConverter. Make methods const as needed. Some general cleanup.

Merge request reports