Problem:
Not all Lua code is checked by stylua. Automating code-style is an
important mechanism for reducing time spent on accidental
(non-essential) complexity.
Solution:
- Enable lintlua for `test/unit/` directory.
- TODO: only `test/functional/` remains unchecked.
previous: 45fe4d11ad
previous: 517f0cc634
refactor: use a more idiomatic loop to iterate over the cells
There are two cases in which the following assertion would fail:
```c
assert(g->icell < g->ncells);
```
1. If `g->ncells = 0`. Update this to be legal.
2. If an EOF is reached while parsing `wrap`. In this case, the unpacker
attempts to resume from `cells`, which is a bug. Create a new state
for parsing `wrap`.
Reference: https://neovim.io/doc/user/ui.html#ui-event-grid_line
