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.
Using fnameescape() for the path argument of findfile() and finddir() is
wrong, as fnameescape() is intended to be used for parts of Ex commands,
not function arguments.
Problem:
On Windows, "gf" fails on a filepath that has a line:column suffix.
Example:
E447: Can't find file "src/app/core/services/identity/identity.service.ts:64:23"
Solution:
- Remove ":" from 'isfname' on Windows. Colon is not a valid filename
character (except for the drive-letter).
- Handle drive letters specially in file_name_in_line().
Fixes#25160
Extend the capabilities of is_os to detect more platforms such as
freebsd and openbsd. Also remove `iswin()` helper function as it can be
replaced by `is_os("win")`.
