We often want to do type checking of public function arguments.
- test: Rename utility_function_spec.lua to vim_spec.lua
- .luacov: Map lua module names
It's a bit cumbersome for us to add an export target every time we define a new function.
It's also cumbersome to care about the order of definition when creating a new function by referring to other functions in the module.
- Rename `meth_pcall`.
- Make `pcall_err` raise an error if the function does not fail.
- Add `vim.pesc()` to treat a string as literal where a Lua pattern is
expected.
This is where "pure functions" can live, which can be shared by Nvim and
test logic which may not have a running Nvim instance available.
If in the future we use Nvim itself as the Lua engine for tests, then
these functions could be moved directly onto the `vim` Lua module.
closes#6580
Justin M. Keyes