[DO NOT MERGE] Feature/3783 replace viper

[dszlachta]

Replaces Viper package with koanf.

koanf is pretty nice, but for writing the file we need to use the underlying TOML library directly. This gives us ability to keep comments in trueBlocks.toml and also the order of settings as defined in Go structure (see src/apps/chifra/pkg/config/write_test.go).

One thing we might want to change is the migration version. If we change it, the users will get comments written in the file.