RpcDigitizationTool -- Introduce checks on identifier validity

Hi,

this MR comprises: *** Clang-format of the RPC_Digitization package *** Declaring class-methods of RPC_DigitizationTool as const where data is obviously just read *** Check that simulation identifiers point to barrel elements and that no BIS8 identifier is actually used. Prompt WARNINGS in the catcher cases *** Update of the test_digi_phase2 script in MuonRecRTT

This MR should essentially remove the crashes in the phase II geometry observed when running over a large number of events. It does not remove the actual cause of the crashes which are wrong identifiers saved in the HITS files.

Tagging: @tadej, @npetters

Closes ATLASSIM-5320, ATLASRECTS-6345