internal/config: migrate local config to `.git/glab-cli`
To set a local config, glab writes to .glab-cli/config/config.yaml
and to hide it, writes to .gitignore
.
This change migrates the local config to .git/glab-cli
to avoid messing with the .gitignore of the current project.
Resolves #791 (closed) #384 (closed)