set buffer name length in buffer list-buffer

customize `helm-buffer-max-length` 
The default length is approximately 20. 
set to `nil` and helm will use the longest buffer name.

Set value using a layer variable 
```
     (helm :variables
           helm-buffer-max-length nil)
```

To configure using Emacs customize
`SPC SPC customize-variable` and search for `helm-buffer-max-length`