bpo-45019: Clean up the frozen __hello__ module. (gh-28374)

Here's one more small cleanup that should have been in PR gh-28319. We eliminate stdout side-effects from importing the frozen __hello__ module, and update tests accordingly. We also move the module's source file into Lib/ from Toos/freeze/flag.py.

https://bugs.python.org/issue45019
12 files changed