Initialize CscIdHelper members in initialize and not during runtime

Hi,

this MR is needed to initialize the m_stripMaxPhi and m_stripMaxEta members of CscIdHelpers already during initialize(). This change can be made, since for all existing ATLAS layouts, there is only one value possible for m_stripMaxPhi and m_stripMaxEta, respectively. This allows to remove 2 mutables and speeds up the code, since the computations is not done during the event loop anymore.

Best, Nico