src: simplify SFINAE of `ToStringHelper::BaseConvert`
Simplify SFINAE of ToStringHelper::BaseConvert
using technique from https://www.fluentcpp.com/2018/05/18/make-sfinae-pretty-2-hidden-beauty-sfinae/
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Simplify SFINAE of ToStringHelper::BaseConvert
using technique from https://www.fluentcpp.com/2018/05/18/make-sfinae-pretty-2-hidden-beauty-sfinae/