Trig::WebBunchCrossingTool Removal, master branch (2020.08.04.)

As discussed in ATR-21827, https://atlas-trigconf.cern.ch now moved behind CERN's SSO. Meaning that this tool is not usable anymore. 😦 If we change our minds about this later on, we will still be able to revive the code from Git's history.

At the same time I brought in some updates to one of the test executables from 21.2. But will use a different commit for enabling that test's build in master. (Once I figure out how exactly I'll want to use it.)

Unfortunately this development lead me down a very deep rabbit hole today. 😦 I spent way too long on understanding why @ssnyder's update in !24269 (merged) didn't actually break the code. As the CxxUtils::get_unaligned functions don't mention anywhere in their documentation that they would be updating the pointers that they receive. 😕 I only noticed this line (for instance) after spending a while pulling my hair out:

https://gitlab.cern.ch/atlas/athena/-/blob/master/Control/CxxUtils/CxxUtils/get_unaligned.h#L65