Function mapArchValidatorConfig

Map an arch-validator config object to layer configs.

• name = layer key (project-relative directory)
• paths = [key + '/**']
• alias = pathAlias (empty string when absent)
• canImportFrom = allowedImports, each mapped to the referenced layer's alias when it has one, otherwise kept as the layer key
• level = level when it is a number (left out otherwise)