LArCoudeAbsorbers+Electrodes: remove lazy initialization of members

Calculate member variables in constructor directly and use const static initialization for singleton. Not only does this remove thread-checker warnings, but it also removes a lot of code duplication and will likely be faster as some of the calculations can be re-used if done in a single loop.

❗ I would really like a careful review by the shifter (even a non-expert should be able to follow the code changes here and make sure nothing got screwed up). Also cc @pavol and @jchapman.

Relates to ATLASRECTS-7235.