MacOS uses a very old version of bash where `"${FOO[@]}"` fails if `set
-u` is enabled and `FOO` is undefined. Newer versions of bash expand
this to zero arguments instead.
Also, `lint.py` used the shebang `#!/usr/bin/env python` instead of
`python3`, which fails on some systems.
In CI, all macos tests run on nscloud runners. Presumably, they have
installed newer versions of various software, hence this didn't break in
CI.
This PR sets up the new integrated test/bench suite. It then migrates
all benchmarks and some related tests to the new suite. There's also
some documentation and some linting.
For now, a lot of the old tests are left alone so this PR doesn't become
even larger than it already is. Eventually, all tests should be migrated
to the new suite though so there isn't a confusing mix of two systems.
