TPC: Processing of common mode values in O2

[tubagundem]

This PR introduces end-to-end infrastructure for reading, processing and storing TPC Common Mode Values (CMVs) within the O2 framework.

New data structures

• DataFormatsTPC/CMV.h — defines the CMV dataformat as received from the CRU: a 256-bit Header (version, packetID, errorCode, magic word, heartbeat orbit/BC) followed by one 16-bit CMV word per timebin, covering 3564 timebins per packet. Includes fixed-point to float conversion helpers
• CMVLinkID = 23 added to RDHUtils.h to identify CMV data in raw RDH streams
• CMVContainer.h/.cxx — accumulator struct for one aggregation interval, storing CMV values together with CRU index, timebin, first orbit/BC, first and last TF counter

New workflows

• CMVToVectorSpec / tpc-cmv-to-vector — extracts CMVs from raw data into vectors
• TPCFLPCMVSpec / tpc-flp-cmv — FLP side processing of CMV data
• TPCDistributeCMVSpec / tpc-distribute-cmv — distributes CMVs and serializes CMVContainer

Compression and size reduction strategies

The following techniques are available for reducing CMV data size:

• Delta encoding
• Zigzag transform
• Varint encoding
• Huffman encoding
• Sparse representation
• Small-value zeroing
• Rounding to the closest integer
• Dynamic Gaussian precision option

Visualization

• drawCMV.C — ROOT macro to inspect and visualize CMV data.

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[shahor02]

Could the class methods with lot of code be moved from the header to cxx file (including needed headers, like TFile.h and TTree.h in https://github.com/AliceO2Group/AliceO2/pull/15137/changes#diff-74cad5f291e0478b7a6334eb7e3dcdabbad615a01df0db129d836a337e76582aR26-R27 ?

[wiechula]

Hi @tubagundem , some minor things and a couple questions:

• How different are the CMVToVectorSpec.h and the corresponding IDC code? Could it have a common base to?
• What is done in the TPCFactorizeCMVSpec.h? I think in the CMV we don't do factorization.