Multiple changes...

[louis-langholtz]

Description - What's this PR do?

• Renames PreStepStats for contacts with prefix of "contacts".
• Moves pre-step updating of existing contacts before the addition of new contacts to improve sensibility of resulting step stats.
• Updates AabbTreeWorld::AddContacts to take the step configuration and finish setting up new contacts, including related manifolds.
• Updates unit testing per these changes.
• Adds new unit test code related to these.

Related Issues

See comments in discussion on serialization/deserialization.

[github-actions[bot]]

clang-tidy review says "All clean, LGTM! :+1:"

[coveralls]

coverage: 99.303%. remained the same when pulling 15a186823d031fae40edd1bf638b9955995481e6 on updates-20231227 into 9b8e702b8e9f5b2481088683170221377e3ee536 on master.