[RM-6643] Make templateCombination inherit from CTemplatefittingBase

Created on 2021-08-05 15:23:08 by Mira Sarkis. % Done: 0

following #6538, the goal is to put in common some fonctions like

• the beginning of compute method
• the method rebintemplate
• the method EstimateLikelihoodCstLog
• ComputeSpectrumModel

note: the private buffers @COperatorTemplateFittingBase::m_templateRebined_bf@ and @COperatorTplcombination::m_templatesRebined_bf @, because in tplcombination this is a vector of buffers, thus the member should be specific in COperatorTplcombination, and thus in the methods we need to split the strictly common part from the specific part, to be ale to overload in tplcombination