lint: Don't use viper global state for config
We have been relying on viper
pulling in the parsed config into its
global config
before our custom linter is loaded. With golangci-lint
v1.57.0 this behavior changed and the config is now empty at the time
of loading.
Remove our custom viper
logic to capture the arguments and instead
use mapstructure
to unmarshal the provided any
config to a useable
struct.