Specifically, functions that are run in the context of the test runner
are put in module `test/testutil.lua` while the functions that are run
in the context of the test session are put in
`test/functional/testnvim.lua`.
Closes https://github.com/neovim/neovim/issues/27004.
Problem:
Processing non-fast events during SystemObj:wait() may cause two pieces
of code to interfere with each other, and is different from jobwait().
Solution:
Don't process non-fast events during SystemObj:wait().
feat(lua): add vim.system()
Problem:
Handling system commands in Lua is tedious and error-prone:
- vim.fn.jobstart() is vimscript and comes with all limitations attached to typval.
- vim.loop.spawn is too low level
Solution:
Add vim.system().
Partly inspired by Python's subprocess module
Does not expose any libuv objects.
