This changeset makes it possible to build the Second Life viewer using
Python 3. It is designed to be used with an equivalent Autobuild branch
so that a developer can compile without needing Python 2 on their
machine.

Breaking change: Python 2 support ending

Rather than supporting two versions of Python, including one that was
discontinued at the beginning of the year, this branch focuses on
pouring future effort into Python 3 only. As a result, scripts do not
need to be backwards compatible. This means that build environments,
be they on personal computers and on build agents, need to have a
compatible interpreter.

Notes

- SLVersionChecker will still use Python 2 on macOS
- Fixed the message template url used by template_verifier.py

merge release@93398 viewer-merge-1@94007 -> release
dataserver-is-deprecated

Hardcoded assumptions that the services were offered on the same host as the region which isn't true for windows development.
NOT TESTED WITH A LINUX SIMULATOR

Fixes the the copy-win-scripts related cmake files to make the copy_win_scripts target function properly.

dataserver-is-deprecated
for-fucks-sake-whats-with-these-commit-markers