WIP: 22.0-cleanup-SiClusterizationTool

Primarily improve error reporting so use of at() with an index out of range is trapped and reports a meaningful ATH_MSG_FATAL message instead of creating an exception (in context of ATLIDTRKCP-302). Other cleanups done: use of cmath constants instead of TMath, tidy up includes, use of std::array instead of a c style array, clarification of the declaration and usage of a pointer-to-member-function variable.

Change to WIP while urgent changes go in (!38018 (merged))