- requirements.txt: shorten copyright headers.
- requirements.txt: pin packages to versions.
- GHA/windows: use `tests/requirements.txt`.
Pick a `cryptography` package version that satifies both `impacket`
and pytests dependencies.
- GHA/checksrc: move pip deps into a new `requirements.txt`.
To make Dependabot detect and bump them.
- GHA/checksrc: replace apt packages for python test deps with pip
install `tests/**/requirements.txt` to a venv.
- GHA/checksrc: use venv and drop `--break-system-packages`.
- GHA/linux: fix to actually activate venvs.
Follow-up to 2638570241#15578
- GHA/linux: fixup (did not cause an issue)
Follow-up to d75785c7de#18660
- GHA: create venvs later, simplify commands.
- GHA: sync pip command-line options, e.g. drop progress-bar,
everywhere.
Assisted-by: Dan Fandrich
Closes#18708